Just FYI, we have been getting similar errors and there is not dots in the file names.
The errors looks always like
[b]ERROR : OPEN OF UNFORMATTED OUTPUT FILE FAILED:
Cannot open the file (invalid path or read/write-protected directory[/b]
and it happens for files with extensions fif, frf, and hot.
Curiously, it happens only at a dedicated xeon-processor workstation (see hardware details at http://www.passmark.com/baselines/V8/display.php?id=35220142111) with Windows 7 Pro. Other I7 PCs have not shown this error so far.