I am getting erratic behavior running viacad under windows vista ultimate 64 bit. the software opens alright but the drawing tools do not work properly. Are there known issues running viacad under vista 64? see attachment and notice how the drawing space does not redraw properly when the mouse is moved around. check the second drawing when I attempt to extrude and the solid does not appear solid. the screen sometimes flashes betwen 2d and 3d when moving the mouse around and clicking the screen the software is unusable in this state. thanks for any input.

To add on to what Tim stated. If setting the compatibilty mode to Windows XP helps, but you still have problems, you can also check the box next to Disable Desktop Composition under the compatibility tab in the properties window.

Also, it is always a good idea to update your video drivers as often as possible.