Getting “No input file specified.” when logging in to admin

I have a site hosted by GoDaddy and used their domain hosting utility for installing WP. Everything was going great until I was ready to make my site “go-live” and followed the “Giving WP Its Own Directory” instructions on here for modifying the URIs and PermaLinks.

I started getting 404 errors and noticed that it was because a / was getting placed after the index.php in my URL. So I went back and tried resetting the URIs, and now not only do my themes not load, but my generated meta links (including admin) are invalid. I can get to the admin login screen by manually typing in the URL, but logging in generates the error message “No input file specified.”, and the panel will not load at all.

I suspect that this could be fixed by logging in to phpMyAdmin, but since I used GoDaddy’s automated installation utility, I’ve no idea how to even go about it. Or is there a different solution? Help!!!