Yet another CAD problem

I use Windows7 64bit and ultravnc 1.0.8.2
UAC is disabled (and i cannot and also do not want to enable it)
If i send CAD during a remote control session, the taskmanager will appear instead of CAD.
If i press CAD on the lokal machine it works as expected.
And taskmanager also only appears pressing ctrl-shift-esc
Anyone else stuck on this problem ?
Thanks for reply