Problem with Taskbar in Vista

Hello,

i have a problem with my taskbar in Vista.

When I start a remote connection from a XP Prof. Client to my
Vista (Ultimate) PC, the connection works, but my taskbar disappears.

I can only see (and use) the round Vista-Start-Button at the bottom of
the screen.
When I close the connection and log on locally the taskbar is still
away.

It only returns after a reboot or a complete logging of and on again.

Is there a problem with my graphiccarddriver?

I'm using a NVIDIA GeForce 6600 GT.
Drivers are from Dec. 2006.

Thank you for any help.
Pascal