UI controls reaction: unduly selection of entries

[lcar]

All interaction using most standard UI controls suffer from an unduly reaction of windows: If I try to select an entry from a combobox I cannot succeed because the dropdown closes almost immediately afer clicking the arrow button. If I try to shutdown windows I even cannot click the combo in the window where to select the action for shutdown - it vanishes in milliseconds!
If I type an URL into the URL text box in Firefox the text is automatically seleted by the system so that the next key entry deletes the text entered before resulting in a malformed URL. This behaviour is annoying.
This does not happen in UI controls embedded in web pages.

I tried to reset my Vista Prof. to a former system state but this failed.
Because the behavior is so strange to describe I did not find any useful hints with Google searches so far.
Any hint appreciated.
lcar

P.S.I notice a frequent flickering of the title bar of all program windows. The flicker happens at intervalls similar to the reaction described above.