I'm having the same problem, but I noticed it after updating Quicktime this month. Various Mac users have reported some other problems on the Apple support forums. Not sure whether this is something Apple or Roxio needs to fix.
I've tried uninstalling Motion Pictures HD using AppDelete, and then reinstalling it. That didn't work. Here's the error message I just received again:
A problem occurred during exporting. It is described as '*** QuickTime failure (-61, /Users/cmeyer/Developer/MP210/LQCommon/LQMovieExport.m, line 350)'.
OS X 10.4.10
QT Pro 7.2.0