I am not sure where this ini file you mention is located, but when you have removed Firefox through Add/Remove programs in control panel, be sure that the Mozilla Firefox folder in "Program files" are removed and that the profile folder in Document settings > User name > Application data > Mozilla, is also removed.
If these two folders are not automatically removed, remove them manually. That should remove every Firefox related file (that I know of anyway).
Then reboot and reinstall Firefox. After that before adding any extension etc, log in to your cpanel and see if it works.
If you can visit cpanel (with visible icons) with that clean install, add one extension, check out cpanel, add one more, check out cpanel and so on. If you suddenly can not view the icons in cpanel, you should by now know what is causing this.