windows vista (late) loading problem

Hi,
I installed windows vista a few days ago and it was working perfectly. then
all of a sudden after a computer restart vista will no longer load up
properly. It gets to the desktop and then the start bar/task bar just stops
and freezes with the loading symbol on it.
Any help is appreciated.

Thanks.

Can someone pleaseeeee help. I am now only able to use my PC in safe mode :_(

Just to let everyone know... the program CA Antivirus corrupted my windows
vista. I fixed vista by removing the programme.