I don't have AC3Filter installed.
MC did install FFDShow the other day, so I uninstalled that but it didn't fix the problem.
If I look in the taskbar the Nvidia decoder icon is there and the logs say it's using the Nvidia decoder, just the volume level is much lower than when I play back the same material recorded to a DVR-MS file.
I tried a channel with AC3 audio rather then MPG and this was the correct volume but the audio is very stuttery and keeps breaking up for some reason, which I'm sure it wasn't when I tried AC3 last time (but can't be 100% sure).
Richard