dmesg will show some errors regarding DMA - I don't have a copy here unfortunately. I was using the 0.1.9 version of the drivers from ivtv.sourceforge.net. To fix this, I followed the instructions at 
http://membres.lycos.fr/badzzzz/ - this details using the 0.1.9 driver set, a 'standard' set of patches commonly applied to 0.1.9, and another one-line patch to fix the DMA issue. It also refers to using a custom ivtv framebuffer X driver, which seems to improve things a lot.
There are probably other ways of doing this, and there are other patches linked from http://ivtv.writeme.ch/tiki-index.php?page=PatchesHowTo which seem to cover the DMA issue as well as 2.6 kernel issues.
No other page links to IvtvNotes yet.
