yes i have windows 7 64 bit latest patches
and latest fences and when i press show desktop
it removes all the fenses and then redraws them
so you see a nasty flicker
ok i think i figured it out
i was running fences and deskscapes at the same time
when i disable deskscape fences runs great
so fences does not work to well with deskscapes 
also it did not matter what type of deskscape even a simple wallpaper caused problems when deskscaes was enabled 