Backup, & reformat your computer. Everything will probably work great then.
Ben600, That's the second time this week you've offered that advice.
This is just my opinion, and I mean no offence to you, but I really don't think it's sound advice to be offering. Formatting your C: drive is not a task to be taken lightly. It's fine if it's something you're used to doing and have a sound backup regime in place, but otherwise, something will invariably get lost forever.
Next, there's all the time and hassle involved with getting windows setup correctly again, drivers etc. installed, software installed, then configured, all of which takes time even if you know where to find every setting and option you need.
Finally, having not understood the cause of the problem, it's all too likely to re-occur in the future making the whole process pretty null and void anyway.
I feel it's a far more prudent approach to seek help with a problem from people who may understand what's going on and be able to offer both steps to fix things and steps to prevent re-occurrance in the future.
For sure, sometimes systems can get so messed up by virii or other such nastiness, or by incorrectly trying to repair the mess made by such that realistically, format C: /u and reinstall windows is the best option, but all other avenues should be explored first.
kevinkr, I had exactly the same problem a few plugin builds ago that went away with a later plugin release. I've no idea if it was a change in the plugin or a change to my system that fixed things, and similarly, at the time I tried every which-way I knew of to get a .dll registered on my computer and none of them worked. It was a very frustrating time which was (thankfully) short lived for me.
I don't have a whole heap of technical advice to offer I'm afraid. I was wondering though, if perhaps you have a real-time virus scanner running? Is it possible that its scanning of the newly copied .dll file is preventing the file from being registered?
-marko.