OK...I rebooted my BES server and watched the logs again.
Right around 16:09:15 I got the "ServerDN not defined" error in the BES MAGT log.
This is what is occurring in the ZCB logs at about that time.
Code:
28-03-2008 16:09:02.912 [3448]: Zimbra::Sync::Synchronizer::TrySync. ++++++++++++SYNC FINISHED++++++++++++
28-03-2008 16:09:02.912 [3448]: Zimbra::Sync::Synchronizer::TrySync. done syncing primary store (Zimbra - BES Admin)
28-03-2008 16:09:02.912 [3448]: Zimbra::Sync::Synchronizer::TrySync. +++++++++++++++++++++++++++++++++++++++++
28-03-2008 16:09:02.912 [3448]:
28-03-2008 16:09:02.912 [3448]: Zimbra::Store::StoreContext::InitiateSync. After sync on store
28-03-2008 16:09:02.912 [3448]: Zimbra::Store::StoreContextManager::ProcessSyncRequest. About to sync other stores
28-03-2008 16:09:03.82 [2384]: In Hook_AddrBookOpenEntry
28-03-2008 16:09:03.82 [2384]: ObjectManager::WrapObject
28-03-2008 16:09:03.82 [2384]: Object Type: (6) MAPI_MAILUSER
28-03-2008 16:09:03.82 [2384]: ctor this(02865898) inner(014150C8) thiscount(0l)
28-03-2008 16:09:03.82 [2384]: Zimbra::Store::ZimbraMailUser::ZimbraMailUser
28-03-2008 16:09:03.82 [2384]: Zimbra::Store::ZimbraMailUser::Initialize
28-03-2008 16:09:03.82 [2384]: Zimbra::Store::ZimbraMailUser::GetProps.
28-03-2008 16:09:03.82 [2384]: Zimbra::Store::ZimbraMailUser::GetProps. (00000000812b1fa4bea310199d6e00dd010f5402000000804200450053002000410064006d0069006e0000004c0053004d0053000000620065007300610064006d0069006e0040007700690075002e006500640075000000) ++++++++++++++++++++++++++++++++
28-03-2008 16:09:03.82 [2384]: Zimbra::Store::ZimbraMailUser::GetProps. (00000000812b1fa4bea310199d6e00dd010f5402000000804200450053002000410064006d0069006e0000004c0053004d0053000000620065007300610064006d0069006e0040007700690075002e006500640075000000) interface address: 14150c8
28-03-2008 16:09:03.82 [2384]: Zimbra::Store::ZimbraMailUser::GetProps. (00000000812b1fa4bea310199d6e00dd010f5402000000804200450053002000410064006d0069006e0000004c0053004d0053000000620065007300610064006d0069006e0040007700690075002e006500640075000000) PR_DISPLAY_NAME: BES Admin
28-03-2008 16:09:03.82 [2384]: Zimbra::Store::ZimbraMailUser::GetProps. (00000000812b1fa4bea310199d6e00dd010f5402000000804200450053002000410064006d0069006e0000004c0053004d0053000000620065007300610064006d0069006e0040007700690075002e006500640075000000) cannot dump the rest of the folder info due to lack of store pointer
28-03-2008 16:09:03.82 [2384]: Zimbra::Store::ZimbraMailUser::GetProps. (00000000812b1fa4bea310199d6e00dd010f5402000000804200450053002000410064006d0069006e0000004c0053004d0053000000620065007300610064006d0069006e0040007700690075002e006500640075000000) ++++++++++++++++++++++++++++++++
28-03-2008 16:09:03.82 [2384]: Zimbra::Store::ZimbraMailUser::GetProps. dumping prop tags requested for this user:
28-03-2008 16:09:03.82 [2384]: Tracing properties...
28-03-2008 16:09:03.142 [2384]: Id(Named Property (8007)) Type(PT_STRING8)
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Rpc::UserSession::GetSupportObject - m_pMapiSup = 0x013d2bc8
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps - # of properties retrieved from profile: 19
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #0 property tag: 0x6640001f
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #1 property tag: 0x66430003
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #2 property tag: 0x6641001f
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #3 property tag: 0x66420102
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #4 property tag: 0x6644000b
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #5 property tag: 0x66550003
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #5 property value: 0x1
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #6 property tag: 0x6656000a
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #7 property tag: 0x6657000a
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #8 property tag: 0x6645001f
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #9 property tag: 0x6646001f
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #10 property tag: 0x66470102
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #11 property tag: 0x6648000b
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #12 property tag: 0x6649000a
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #13 property tag: 0x6650000a
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #14 property tag: 0x6652000a
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #15 property tag: 0x6651000a
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #16 property tag: 0x3d0c000a
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #17 property tag: 0x3d12001f
28-03-2008 16:09:03.142 [2384]: DEBUG: Zimbra::Mapi::GetProfileParamProps #18 property tag: 0x66580003
28-03-2008 16:09:03.142 [2384]: Zimbra::Store::ZimbraMailUser::GetProps. preprocessing prop tags found PR_EMS_AB_HOME_MTA at index 0
28-03-2008 16:09:03.142 [2384]: Zimbra::Store::ZimbraMailUser::GetProps. the mail server is zimbra.xxxx.edu
28-03-2008 16:09:03.142 [2384]: Zimbra::Store::ZimbraMailUser::GetProps. MDB string is /o=zimbra.xxxx.edu/ou=First Administrative Group/cn=Configuration/cn=Servers/cn=zimbra.xxxx.edu/cn=Microsoft Private MDB
28-03-2008 16:09:03.142 [2384]: Zimbra::Store::ZimbraMailUser::GetProps. MTA string is /o=zimbra.xxxx.edu/ou=First Administrative Group/cn=Configuration/cn=Servers/cn=zimbra.xxxx.edu/cn=Microsoft MTA
28-03-2008 16:09:03.142 [2384]: Zimbra::Store::ZimbraMailUser::GetProps. populating PR_EMS_AB_HOME_MTA with ansii at index 0
28-03-2008 16:09:03.142 [2384]: Zimbra::Store::ZimbraMailUser::GetProps. dumping prop values returning for this user after mapping.
28-03-2008 16:09:03.142 [2384]: Named Property (8007) PT_STRING8 /o=zimbra.xxxx.edu/ou=First Administrative Group/cn=Configuration/cn=Servers/cn=zimbra.xxxx.edu/cn=Microsoft MTA
28-03-2008 16:09:03.142 [2384]: Zimbra::Store::ZimbraMailUser::GetProps. exitting early
28-03-2008 16:09:03.142 [2384]: Zimbra::Store::ZimbraMailUser::~ZimbraMailUser
28-03-2008 16:09:03.142 [2384]: dtor this(02865898) inner(014150C8) thiscount(0l) innercount(0l)
28-03-2008 16:09:07.118 [3456]: TRACING => ProgressTask::~ProgressTask this(0x27a6b60)
28-03-2008 16:09:58.591 [3504]: *5* ERROR: Zimbra::Rpc::Connection::SendRequest - failed on WinHttpReceiveResponse(...), Error Code: 12002
28-03-2008 16:09:58.961 [3504]: Zimbra::Store::CWaitRequest::WaitRequestThread. SendRequest failed with Error 0x2ee2. Desc The request has timed out.