That could be a possibility though the origin of the files are not known.
I received them from a customer back in 2005 for testing some macros when I worked for Siemens as an A.E. In that case I should have got the error at that time itself.
I updated the 10 year old macro recently and was trying to test on the same old files from a CD backup using ST6. For a moment I thought it was some data corruption when reading-writing from the CD. The files open fine though.