Hi again!
I know this is technically necro-posting seeing as this topic has been motionless for about a year now, but i thought you might want to hear an update to this situation.
So here's a recap of what happened. For years i had been using PDN without problems. But suddenly, at the end of last year, my v3.5.11 stopped working for no apparent reason (although i suspect that a recent Windows Update had something to do with it, which is why WU will NEVER be run on this computer again).
I tried uninstalling and reinstalling PDN, but to no avail. A couple of weeks ago, after a year of occasional searching for a solution, i realized that the problem all along was that i was unable to completely uninstall my corrupt v3.5.11 from my system. And because i couldn't uninstall the faulty version, i was unable to install a functional version.
After checking the "Install/Uninstall Problems" topic, i came across some utility by Microsoft that can forcibly uninstall a program (i think it's called "Microsoft Fix it"). This utility successfully uninstalled the faulty v3.5.11 from my computer, and i was able to successfully install a much older version of PDN from 2008. I tried opening it as usual, not expecting it to work, and i couldn't believe my eyes when i saw PDN open for the first time in over a year.
So this story had a happy ending.