MPEG-4 stopped working on Vegas Movie Studio PE 7

[OakBloodThree]

I know it's an old version of Vegas, but please bear with me:

I started editing a new project in Vegas Movie Studio Platinum Edition 7.0a that included some public domain footage from archive.org.

The audio came in OK. Video came in like a psychedelic "posterize" effect-- the color pallete was shifted so you could only make out shapes and motion but there was a weird mixture of colors. Every other frame is black.

I thought it was a problem with the source media file, so I opened an old project to check. I found the same problem in all MPEG4 media (example of one here: http://www.archive.org/details/hazards_of_helen_wild_engine).

That old project included some media that came from my miniDV camcorder (AVI) alongside the MPEG4 file above. All the camcorder footage looks fine and other Vegas functionality is OK.

No CPU hardware changes have been made since this last worked (though I did get a new LCD monitor to replace a CRT), and no major software changes (just Windows & Antivirus updates).

I tried removing Vegas, deleting all its registry and Application Data, and reinstalling but it didn't help.

The file above is H.264 encoded, and plays OK in QuickTime.

Any idea why my system lost the ability to process these files?

[poisondeathray]

Try installing xvid codec
https://www.videohelp.com/tools/XviD_Codec

EDIT: I didn't see your edit. If it's h.264, then installing xvid won't help you. (I assumed MPEG-4ASP when you said "MPEG4")

Did you upgrade quicktime recently ? If so, downgrade to an older version like 7.4.X , many vegas users have had problems with the recent quicktime versions

[OakBloodThree]

Thanks!

After my last post I noticed that some files even crashed Vegas, and the offending process in the debug window was part of QT.

I rolled back to 7.4.5 and that did the trick.

(I didn't actually update QT intentionally. Auto-update is off now.)