When I run memtest86 on this setup, there is always an error at two
locations on this stick, no matter what timings I have tried. Mind
you, before I updated the bios there were some other flaky things
happening here (i.e., XP only acknowledged 256MB of the 1 GB to exist,
although other programs such as CPU-Z would list at 1 GB). But only
memtest86 has ever given me a problem here. I have another memory test
that runs under XP, it will run all day w/o error. If I do not
overclock, Prime95 will run all day with no error.

Can I just use this stick w/o problems?

Not in the long term. It isn't easy to predict the consequences of memory
errors because the nature of the error will depend not only on the failure
itself, but the type of data stored when the failure occurs, and the usage
of that data. If that spot in memory was supposed to hold one bit in a .bmp
file, nothing's going to happen. If it's holding an address pointer, you're
screwed.

Overall, though, it's safe to say that errors *will* crop up, at least
occasionally.

steve