thanks for your replies
I did the normal windows updates, yes. so all computers have the same (new) patch level. i'm not sure if i wanna revert and stay on an older patch level.
but maybe we can even get the directshow drivers to work?
-- merged --
ok, update... at least on one computer i could solve the mystery (i guess it would work on the others as well):
in the hauppauge driver (video > capture filter) i could set the video mode.. in the past, i set it to PAL-B which was obviously not correct (Germany)... as soon as i set PAL-D, it worked fine. i can capture again. and i can switch to WDM again
for google: the symptoms have been, that i could capture with my hauppauge driver, but i got a video without video-information (like 10 mb/min). even the vdub stats on the right didn't do anything (no frame counter, no nothing). whenever i switched to the wdm driver, vdub crashed.
thanks again for your help.
*** SOLVED ***