This is an unknown disk error of the type given above. Try mailing me at David.Shaw@acm.org and telling me what you were doing when you got this message.
Your disk is full. Try another disk.
Your disk is write protected. Try un-protecting it.
This disk is locked. Try unlocking it.
I do not have permission to write to the output file.
It is possible (likely?) your input file is damaged in some way. Try another file.
The output filename is already in use, and I cannot seem to make up an alternate filename.