I tried installing a fresh copy of R5F27 from scratch today but found myself stymied @ the capture card setup screen.

I've installed knoppmyth several times, and never had this problem.

When i chose the MPEG-2 encoder card (PVR-x50, PVR-500), the video device and default input select boxes were blank, and "probed info" read 'failed to open'.

This failed to open message was repeated for a number of other input cards as well as i cycled through the card type.

previously, the pvr-250, the card i have, worked great right away.

Anyone have any ideas or how to point me in the right direction?

What do the log files say? http://www.knoppmythwiki.org/index.php?page=CheckingLogFiles

Have you monkeyed with the hardware or moved the machine recently? Have you checked that the card is properly seated and the like?

Just finished posting my thank you for help on this exact problem. Ended up that the card had come lose when I moved the box.

Try re seating the card before you start going thru log files.

Double checking the physical connections is almost always good advice, but I still recommend checking the logs first, since it's generally easier to check the log files than to tear the box apart and check the card...