A bit more additional information. I've installed winhttptrace and as I'm seeing HTTP timeouts for the following requests:
POST /service/admin/soap/ HTTP/1.1
Content-Type: application/soap+xml; charset=utf-8
User-Agent: Zimbra-ZCB/5.0.2428 (5.2.3790 Service Pack 2; en-US)
Host: zimbra.server.com:7071
Content-Length: 1119
Connection: Keep-Alive
Cache-Control: no-cache
Pragma: no-cache
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope"><soap:Header><context xmlns="urn:zimbra"><userAgent name="ZimbraConnectorForBES" version="5.0.2428"/><nonotify/><noqualify/><authToken>BIG_LONG_STRING72613b6d61696c686f73743 d31343a31302e32302e3132382e333a38303b</authToken><nosession/></context></soap:Header><soap:Body><WaitSetRequest xmlns="urn:zimbraMail" waitSet="WaitSet35" seq="6" block="1" defTypes="all"><add><a id="IDHERE6380" types="all" token="765"/><a id="IDHEREed9dc" types="all" token="122823"/><a id="IDHEREbc163d119d7" types="all" token="367921"/><a id="IDHERE068ee" types="all" token="413971"/><a id="IDHEREdb3e5af9657" types="all" token="11886"/><a id="IDHEREa706" types="all" token="260945"/></add></WaitSetRequest></soap:Body></soap:Envelope>
I'm unsure if this would be related or not.
Thanks,
John