Without checking the code I'm almost out of ideas.
I've tried disabling all 3rd party modules, didnt seem to do anything, but i'll do it again and confim.
This is pretty much a basic installation, with few very mods.Is it possible to reupload the core files of magento without affecting anything? If so, which ones would i replace?
If you didn't change the core you can re-upload the files and you shouldn't get any problem.
I can't guess if that is the reason of the issue.