Thanks CTAHOK. That solution got me going in the right direction. It would seem to me that the length of the time out is different between the web and thick client.
In my case, I was able to resolve the issue in my environment (vCenter 5.1.0 Build 1123961) by modifying the Base DN for users and groups to: OU=<ORGUNIT>,DN=<DOMAIN>,DN=<LOCAL> (where ORGUNIT, DOMAIN, and LOCAL are replaced with environment specific details).