memtest from F17 beta DVD images
I booted the F17 beta ISO (x86_64, if it matters) on two laptops and
tried the provided memtest. In both cases it reported insane amounts of
errors in test 7 after running successfully through tests 1..6. The
reported error addresses are in the 120 MB area.
I checked that when memtest is configured to go directly to test 7 the
errors appear right away.
I have not had the chance to retest with older images but the chance
that both laptops independently developed RAM problems in the same area
seems small. I'll do more tests and file a Bugzilla report if it checks out.