Hmm. I still can't seem to get 1.7.0.6 to install properly. Like the poster above, I get an "upgrade available" message every time I start, and About says I'm still running 1.7.0.4. I'm pretty sure it's not just showing the wrong version number, because the Mastermind Epic power selection bug you fixed in 1.7.0.6 is still there.
I tried all of the things mentioned upthread, and scoured both my filesystem and registry for leftover stuff before reinstalling. Didn't help.
Any ideas?