Windows 7: Can't set Firefox as default image viewer

Hello, long story short (not really that short but) I have two versions of Firefox on my computer Firefox (13) and Nightly (beta) I had to uninstall nightly due to a bug and reinstalled it and it was working fine except I noticed that the image file types associated with it were no longer defaulting to anything. I thought this would be an easy fix (right click > open as... set it to the default for that file) but whenever I click either Firefox or the nightly exe nothing happens..

I then decided to go to default programs and set association but the same dialog as open with came up and the same thing happened. I'm not really sure why it is this is happening but here's some info that could help you help me (if you're feeling nice

1. This all started after I uninstalled the Nightly build
2. The nightly build I was using before was 64 bit and the one I am using now is 32 bit
3. The two versions are both 32 bit
4. You can't open the two as separate programs, clicking the firefox exe with nightly already open will just create another nightly window and vice versa.
5. It's not just image files, you can't default any file type to firefox.



I hope someone out there with more knowledge than me can help me with this, I would be very grateful. Thanks!