I have Zimbra 6.0.10 on a Ubuntu 8.0.4 LTS x64 and I have a problem with some user that use zimbra webmail from a win 2003 x64 with IE8 full updated (windows and IE8)

The problem occurs randomly when users connect to RDP to the server and access the zimbra webmail, at this moment the cursor pointer constantement dle is changing hands clock constantly and seems to work more slowly. On the server side can see a higher than normal load

Error that appear in the logs is :

[btpool0-17://server/service/soap/SearchRequest] [name=user@domain.com;;mid=4246;ip=;ua= ZimbraWebClient - IE7 (Win)/6.0.10_GA_2692;] soap - SearchRequest

This also happened with Zimbra 5 and explorer 7, and after the upgrade continues happening. The odd thing is that happens randomly and sometimes on a server and sometimes in another, but not always in all terminal server

Resolved or restart the terminal server or a few hours in which users have closed the session. Rebooting the Zimbra server is not resolved

What could be causing this? How I can solve?