This same thing literally just started happening to me. Haven't loaded anything new or recent in a while, but also haven't used Vectorworks heavily in the last few months.
Could this be another of those Quicktime related bugs?
Running Vectorworks 2009 on:
Windows Vista 64 bit
ASUS P5Q Pro P45 Mobo
Intel Core 2 Duo E8400 3.0 Ghz
Asus Radeon HD 4850 512MB
Corsair Dominator 4GB RAM
Corsair 650TX PSU
Thanks for any help