"Check disc for defects" (run on a different computer than the test system) reports no errors.
I booted from a CD, chose English, and selected "Try Kubuntu without installing". After ~10 seconds the screen flashed on and off repeatedly, then stayed in the black-but-powered-on state. Eventually I heard the KDE start-up sound. The screen did not light up when I tried moving the cursor or pressing keys. Ctrl-Alt-F1 and Ctrl-Alt-F7 did not switch to other TTYs or sessions.
The test computer is an HP Elitebook 8440p model WH255UT#ABA. Chipset: Mobile Intel QM57 Express, graphics: Intel Graphics Media Accelerator HD.
Note especially that this computer _does_ boot up successfully with a year-old Xubuntu 9.10 Live CD.
00:00.0 Host bridge: Intel Corporation Core Processor DRAM Controller (rev 12)
00:02.0 VGA compatible controller: Intel Corporation Core Processor Integrated Graphics Controller (rev 12)
00:1f.6 Signal processing controller: Intel Corporation 5 Series/3400 Series Chipset Thermal Subsystem (rev 06)