I got the above error today after running Windows Update on my XP VM a few days ago. A quick search showed that the error is caused by a Microsoft update to the .NET framework. To resolve it, remove update KB980773 (Add/Remove programs, make sure “Show Updates” is checked; KB980773 is under “Microsoft .NET Framework 2.0 Service Pack 2”). I removed it and was able to log in without problems.
References:
- http://communities.vmware.com/message/1553296#1553296
- http://www.experts-exchange.com/Software/VMWare/Q_26251559.html
Edit 10/22/2010: You can also resolve this by upgrading your vCenter client to 4.1, which I recently did. 4.1 is available on vmware.com.
Evan Hoffman's Blog 
This solution worked great. Thank you. Just don’t understand why other computers with the same update works fine.
Thanks! This worked perfectly. Later after I did your solution I found this solution although I like yours alot better. Yours is easier and quicker…less aggressive than the one posted by Vmware themselves.
1) http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1022611
2) http://communities.vmware.com/message/1562425#1562425
Thank you so much. It works perfectly now.
Hiya. Struck this myself – even easier way is to uninstall the viclient and reinstall it. That way you can keep the .net update & have the viclient working.
Thanks much for this solution! Works great, and much easier than all the other solutions I’ve come across (just like the others who commented here).
Worked for me, thanks! Seems like every couple of months Microsoft releases a patch that breaks this. Thanks for figuting it out!
On the plus side, when I got hit by this again recently (out of nowhere) it pushed me to upgrade to vCenter 4.1 & update all my ESX hosts to 4.1 (was still on 4.0.0). With the 4.1 client there’s no problem.
Yes, this is what I needed. Thank you.
Thank you very much. perfect solution.
I verified the patch availability and confirmed taht it didn’t to be found on the computer running windows 2003 x64bits. Kindly let me know if anythin else apart from the above solution needs to be checked in order to solve this issue.
Kind regards,
Rakesh