https://bugs.freedesktop.org/show_bug.cgi?id=83810
--- Comment #2 from Glenn Kennard glenn.kennard@gmail.com --- The weight paint not showing was fixed by https://bugs.freedesktop.org/show_bug.cgi?id=81967 which will be included in the 10.3 mesa release (isn't quite out the door yet though).
Three questions: is it a 512MB or 1GB 5770, and how much system RAM do you have? Do you get any messages in dmesg while running blender?