I am using OVSD client 2008 version 4.5 on windows 7 machine. After a fresh installation everything was working fine. However, since past couple of weeks I am facing issues with it. When I try to open it, the credential window doesnt come up and it closes out completely.
I tried the following option c:\regsvr32 "c:\msado15.dll" by getting the dll from Windows vista and running regsvr32 in Vista compatibility but without any gain.
No clue about your specific issue but I recently learned of somebody who had client 2008 working fine and a couple of weeks later started acting up. In the end, the box was re-imaged and client 2008 worked fine again.
We suspected Windows Updates, as this was the only thing that made any system changes in the workstation.