Hauppauge TV tuner and no video. Anyone?

[Bogdan]

I haven't gotten any response to my previous post so I'm reposting it with
some more info and hope that someone will have some ideas.

I can't make Hauppauge HVR-1270 tuner to work reliably on XP. Quite often I
get only audio and no video. I'm using VMR7 in windowless mode for
rendering. I also tried old VR with same results.
I compared graphs when the video was showing and when it was not. In both
cases graphs were identical.
They looked as follows (crossbar not included):

Hauppauge WinTV 885 Video Capture -> Smart Tee -> AVI Decompressor -> Color
Space Converter -> VMR7.

The audio seems to play fine when the video is not showing. Channel
switching also works fine.
The tuner is running in analog mode with cable input.

Could someone please give me some idea what I could try to make it to work?
Or, is there another group/blog more suitable for this post?

Thanks,
Bogdan