Slow USB flash drive on Vista

Hello group members,

After installation of some software on my fresh install of Vista x86,
I have trouble reading and writting to my USB flash drive efficiently:
it takes me 4 minutes to see the context menu pop up when I right
click a file on the flash drive, and it takes 30 seconds to response
to a delete click by firing up a question dialogue box, copying a 15Mb
file takes 10-15 minutes.
The particular USB flash drive works blazingly fast on my other XP
machine. I tried reformatting it, and it performs the same with these
issues on Vista.

Here are some other symptoms:
- The Vista machine read and write on my other USB hard drive (not
flash) without any slowing problem.
- Some time, the USB flash drive responses reasonably fast every time
when it is first plugged in during its first 20-30 seconds, and then
it becomes painfully unusably slow.
- *** I booted into SAFE MODE of Vista, and the USB flash drive reads
and writes as fast as it does on my other XP machine.

I really want to locate the origin of this particular problem. I tried
"tasklist" and "tasklist /svc" to scan processes before and after
having the USB flash drive plugged in (in Vista Normal mode), and have
discovered nothing special. Can use some other tools in sysinternals
(e.g. process monitor / process explorer) to locate the origin of
problem?
Please point me to how I can do that... Thanks!