QTR-Quadtone RIP

Hi. I've been using QTR for a while now -- no problems to speak of.  Now all of a sudden, I can't print anything at all ?!  Every time I open a tiff & click "print", I get an error message saying "File Access denied" ??   I'm able to print the same files on my Canon i9900, but not on my Epson R1800.  Anybody have a clue ??  Thanks much, Pete