moliones,
It looks like (at least for the ffh264vdpau case) you've been hit by one of the bugs described in this thread:
http://www.nvnews.net/vbulletin/showthread.php?t=130690
I'm not sure if your ffh264 case is related to this or not.
We'll add you information to the list of problematic HW. Reproducing this and fixing it is one of my highest priority items. however, so far it's been impossible to reproduce...