Alright, basically IE is a huge piece of shit which doesn't implement the <button> tag correctly so anyone who wants IE compatibility has to implement annoying workarounds for what should be the simple task of submitting a value to the server through a button (it submits what the button displays, in this case the url of the button image, instead of the coded value of the button).
ANYWAY, after a lot of research and trial and error trying to figure out what part of the spec IE implements correctly, I've come up with a fix that seems to work in both Safari and IE7. I don't have a copy of IE6 to test it in, if anyone wants to test that for me.
If you had the previous version, just overwrite ucp_favorites.php with the new version and it should be fixed for both prosilver and subsilver2. Download link