audio disappears in vegas 8(a/b) for some mpeg4 imported files
 

anyone seeing this problem?

REPRODUCTION STEPS:
import certain mpeg4 video files onto the timeline, then the audio stutters then disappears. this is for ALL audio tracks in the project; even ones that previously worked. i'm annoyed that i can't seem to find out what underlying video codec is used, becasue i think mpeg4 is a generic wrapper. vegas is reporting the audio as 48khz/16 bits, but it doesn't specifically say pcm. media info says 384kbps 2 channel pcm, which makes no sense to me since this is too low.

if i remove the offending video clip, makes no difference: audio playback is dead. i need to close the project then reopen a new one for audio playback to work again. however mixdowns have the proper audio.

the strange thing is that the vegas audio output bus meters continue to show audio activity, but my rme audio driver meters show nothing.

i'm using winxpsp2 and an rme hdsp unit with wdm drivers. this is a 3ghz quad-core box with 4gb of memory. and i've been using vegas since version 4 and haven't seen this problem.

I think this is a newly introduced bug
 

with the last build, I notice now when I preview material using the explorer tab with auto play turned on, I get no audio now, whereas before no problems.