https://bugs.freedesktop.org/show_bug.cgi?id=94414

--- Comment #12 from Felix Miata mrmazda@earthlink.net --- (In reply to Jean-Philippe Gariépy from comment #11)

I'll try using another desktop environment tonight.

Not just another DE, but another OS, like a Knoppix DVD or other live media, to help determine whether a software problem, or failing X300 RAM. If it's RAM, maybe trying a lower resolution mode or display would tell that your real limit has dropped to less than 2048. Was your X300 manufactured by MSI, or shipped originally in a Dell PC?