8.26.18 (32-bit) drivers seem to have fixed the problem for me, now. Card details are as follows:
0000:01:05.0 VGA compatible controller: ATI Technologies Inc RS480 [Radeon Xpress 200G Series] (0000:01:05.0 0300: 1002:5954) -- Lockup problems with both the free xorg ATI driver and the proprietary fglrx driver, using various ATI cards https://launchpad.net/bugs/30447 -- kubuntu-bugs mailing list kubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/kubuntu-bugs
