Hi there, i just had the same error in MDT2009 while using hte PLOT command (QSAVE also triggered the error btw.)
The issue was resolved by typing SAVE in the command prompt, save as new file, close MDT and reopen the saved file. (as per Steve's post)
Thanks a lot
Start with some of our most frequented solutions or visit the Installation and Licensing Forum to get help installing your software.