QTR-Quadtone RIP

I have been using QTR with great success for the last year or two  and it's 
always worked great for me. But since yesterday I have been  experiencing 
an odd problem - suddenly I cannot open any of my  Image Files.
 
I'm running Windows 7 professional 64 bit on a fairly powerful PC and have  
been using QTR version 2.7.0.0. 
 
I hadn't used QTR in a month or two and a couple days ago I opened the  
program to print several new images. Program opened fine and I clicked on  File 
> Select Image. The "Open an Image" window came up but when I tried to  
select my image file, the program froze up and become non-responsive for a  
minute or so. Eventually I got a message box that says ""Quadtone RIP Front End 
 is not responding."
 
Repeated attempts to open image files yielded the same (non) results.
 
The main interface seems to be working fine - I'm able to see and adjust  
all my drop-downs for paper preferences, curves, advanced adjustments, etc -  
it's only after I try to select an image and that window opens that 
everything  freezes up. The "Open an Image" window is completely non-responsive - 
the folder  I have always designated for my QTR images shows in the drop-down 
menu, but  clicking on the dropdown does nothing. And even though the 
dropdown lists  that folder, none of the images that are in the folder (all of 
which I have  printed via QRT before) are showing up - the space is blank.
 
I've searched the past postings of this group but couldn't find anything  
referencing a similar problem. So far I've tried all these remedies, to no  
avail:
 
1) Closed QTR and Rebooted Computer
 
2) Downloaded and installed version 2.7.6 of QTR for Windows
 
3) Deleted both my original 2.7.0.0 and new 2.7.6 versions of QTR - then  
once again downloaded version 2.7.6
 
I'm a little reluctant to try a Windows "System Restore" to an earlier  
date, but right now I cannot think of anything else to try. 
 
Any help would be much appreciated.
 
Thanks,
 
Rob McKay