SP1 - Switch User no longer works

Can anybody help me.

After installing SP1 via Windows Update the Swith User facility no longer
works. My PC tried to load the new user's desktop but gets stuck without
completing the process (icons don't appear in the system tray, the sidebar
doesn't appear) so that none of the programs or icons work.

Logging on and off still appears to work.

TIA. John.

I'm having the same issue. It doesn't matter which of my two user accounts I
log into first -- the first one loads fine and the second one never finishes
loading (most noticeably the sidebar gadgets, wallpaper, some icons, etc.).
I'm using Vista x64 with SP1.