Audacity not showing waveform, x64


I have been a user of Audacity for a few years (including compiling with ASIO) on XP. However I have a Laptop with Win 7 64 Home Premium and no whater which version of audacity I install (2.0 or 1.3.x with or without ASIO) I get the same show stopper. If I try to import a simple wav I get either no waveform drawn (just the diagonal lines) or a straight line (even when zoomed in - every sample is zero) or if I try to generate a tone or noise I get the same straight line. If I try to use the draw tool the samples will not move. Installing latest Realtek 64bit drivers from Realteks site makes no difference. Audacity has been removed, ccleaner run, registry cleaned, reinstalled lots of times with no difference. Needless to say I get no audio output! (Audio works fine in all other applications)

Anybody got any ideas?

The first thing that I would suggest is resetting Audacity Preferences: