Vista - problems with Readyboost?

I just recently bought a SonyVaio VNG NR180E notebook. I've been trying to
use a PNY Readyboost flash drive with the computer, but often when I try to
click on that drive in My Computer, the computer will freeze up, or is very
slow and unresponsive. The same thing happened a few times when I tried to
click on the DVD RW drive. I called Sony support and they told me to run my
antivirus program, run the disk defragmenter and cleanup utilites, and a
hardware diagnostic test. Since then, the DVD RW drive hasn't had any
problems, but I'm still having the same problems with the Readyboost flash
drive. I tried another Readyboost flash drive, which seemed to work better,
except when I allowed the computer to go into Sleep mode with the drive in,
when I restarted the computer, the Readboost file seemed to have disappeared
when I clicked on the drive in My Computer. It reappeared when I formatted
the drive over again. What I'm trying to figure out is are these problems
caused by Vista's readyboost feature, or are they being caused by defects in
the computer or flash drive I'm using. Does anyone know if any of the
problems I've described have been associated with Vista's Readyboost feature?
Thank you.