Can you verify if any of the following are applicable:
https://www.ptc.com/appserver/cs/view/solution.jsp?n=CS77509
https://www.ptc.com/appserver/cs/view/solution.jsp?n=CS56366
http://www.ptc.com/appserver/cs/view/solution.jsp?n=CS62243
If those don't yield any helpful results it may be a good idea to generate a Windchill profile or use the MS SQL Server tools to verify whether there is any long-running SQL causing the problem. It may be necessary to create/change some indexes to help improve performance.
I assume that this occurs in both standalone and embedded browsers?