Guest virtual drive erroneously dismounted from OS X

I am trying to access a file on the C drive of my virtual machine. I have enabled sharing windows in the parallels configuration menu (I checked 'Access Windows folders from Mac' and 'Mount virtual disks to Mac desktop'). When I try to load a file from an OS X application that resides on the C-drive, I can navigate the drive, but as soon as I try to load the file, I get a message indicating that the file cannot be found. I then look in the finder and see that the drive is no longer mounted.

I'm trying to access a .dll in C:/Windows/System32/ and I notice that when I try to view all files in that folder (there are many of course), the program hangs a bit. I suspect that some kind over overload on the virtual drive interface during this process is causing it to dismount.

I'm running Win7 32-bit on Parallels 7 on OS X 10.6.8. The program I'm trying to point to a .dll with is labview, and the interface for selecting the file seems to be custom (i.e. not native to OS X).