Issues sharing a briefcase to external users

[sgrzy01]

When we share a briefcase with an external user with View rights and a user/password... when the user receives the share e-mail and clicks on the link, they get the following right away... there is no prompt for a user/password...

Link in the email is:

https://zimbra.XXX.net/home/jack@YYY...E%20Dilligence

The Error is:

HTTP ERROR: 403

permission denied: you do not have sufficient permissions

RequestURI=/service/home/jack@YYY.com/S DUE Dilligence

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Domains has been replaced with XXX and YYY to protect the innocent... but note they are different...

Thing is... sometimes it will work... most times, it does not....

Also, user has other briefcases that initially gave us this same issues, but work fine now...

Cannot find anything in the logs either to see what is happening...

Our users are beginning to "discover" this feature, so I'd like to get a handle on this issue now...

Any ideas on what I am misssing?

Thanx...

Zimbra 5.0.18 on CentOS5