Comment 9 for bug 375224

Some of you might try the following (taken from http://www.gossamer-threads.com/lists/mythtv/mythtvnz/378788#378788):

Try putting the following in /etc/sysctl.conf

vm.min_free_kbytes=16384

Also [depending on] how many analogue cards do you have as you might want to double the value to 32768.

The ivtv driver tries to compensate for a lot of bugs in the dma chips on the 150/500 series cards but sometimes it isn't enough. When it gets really bad a reboot is generally recommended.

Other ideas:
http://ubuntuforums.org/showthread.php?t=899947
http://www.gossamer-threads.com/lists/ivtv/users/35808#35808

If this resolve the problem for you, please be sure to report back here!