I am having just an awful time with Parallels on my iMac (version 10.6.4). Bought it several months ago (version 5 now), and it has been next to useless. It is exceedingly slow most of the time; literally can take 30 minutes to open a program like Quicken. Occasionally this is resolved by restarting the Mac, but not always. Honestly I use it primarily for Quicken, because some of the financial institutions apparently don't know that there are plenty of Mac users out there. Anyhow, does this sound like something a reinstall might help? I have updated Parallels, with no improvement. Overall, I think this was a complete waste of my money. Not at all as advertised.
How much memory does your iMac have? If your RAM is not maxed out, then you should get more. How much memory did you assign to your VM? How many CPU cores does your iMac have? How many did you assign to your VM? How much VRAM did you assign to your VM? What kind of graphics card does your iMac have? Where is your VM hard disk located? Try adjusting the options in Configure -> Options -> Optimization. Press the ? button to read what the options do.
