I am rushing to get a project finished, but DVDA 4.5c is complaining that

"one or more of the file plug-ins necessary for preparing the DVD is missing or corrupt"

A re-install has not fixed the issue.

I am simply importing an uncompressed .AVI out of Sony Vegas 7.0d and trying to burn a single-movie project.

Any ideas? Fed-Ex deadline approaching...

Why feed it an uncompressed AVI?
My guess is that's where the problem lies.
DVDA prefers to see properly encoded MPEG-2 + AC-3 streams or regular DV-AVI.
If it's 70 min. or less, use a CBR of 8,000,000 or a VBR of 8,000,000 / 8,000,000 / 4,000,000
If it's longer than this, let us know the length and we can tell you the proper bitrate.