I was going to say Web Assist people will probably catch this thread and contact you personally, but I guess Jason was quicker than I was. :) I suggest you give them a try. They really are helpful, and I can testify that from my two year experiences with them. (I have a SuperSuite license.) I know it's irritating, it always is for me whenever I have trouble with this sort of thing but as far as WA stuff is concerned they've been pretty good with support and overall functionality of their software. Even PowerCMS has already been worth the initial trouble for me once I got it resolved in my case.
FYI, it seems like it is often the DW site setup not completely filled out or filled out with "incorrect" parameters when PowerCMS doesn't respond at all. In my case, PowerCMS didn't do anything at all just like in your case at first, and it turned out that it was a blank URL Parameter under Test Server section. I set up my DW site so that Local, Remote and Test server sections are completely filled out including URL Parameter. I also set my Remote site "Local" since it was a test site and I didn't have the actual FTP server. Not sure if that matters, though.
Also make sure your site root folder's permission is set to 777. It might not have to be 777 but that's what worked for me to avoid the error in PowerCMS installation script (run via browser when CMS region insertion is complete). If you forget it will get stuck at step 3 and say PowerCMS/Connections folders don't have write privilege. You actually won't find those folders so simply create them and set them to 777:
You can set the permission via local pane of your FTP program.
If you are using a test server such as MAMP/LAMP/WAMP, I would make sure (just in case) your test site domain is set to handle both "www.(domain).com" and "(domain).com" without www. Might not have anything to do with this problem but URL Prefix seems to affect PowerCMS and thought it could cause some issues depending on how the server is set up.
Reinstallation, reboot, etc. most likely won't help. In general, I've found that such procedure except deleting .dat file has nothing to do with DW extension problems. In the past nearly 100% of the time it was something else that solved problems.
I hope WA will fix these problems ASAP. All this being said we really shouldn't have to perform workaround like this. It should just work out of the box without figuring out these things.