If you've followed my blog, you'll know that my experience with ReadyBoost has been painful. The most recent problem has been that the Apacer HT203 thumb drive isn't recognized as a USB 2.0 drive. Whenever I plug it in, Vista (or Windows XP on another system) gives the error that the "drive would perform better if plugged into a high speed port." Since Windows thought the device was USB 1.0, ReadyBoost wouldn't work at all. This fixed the hanging problem, but not the way I intended.
Previously, I had written Apacer to try and get help with the system hangs. Apacer technical support did finally respond. They hadn't heard of my problem before (predictably) but gave me a utility to low level format the drive, which I tried but it didn't help. (Note: it costs about $15 in postage, round trip, to send a thumb drive to Apacer for repairs. My recommendation - if the drive is 1GB or less, throw it away and buy a new one.)
Tonight I was tinkering with the drive again and tried to format the drive in Windows, just for chuckles. At which point I realized that Windows had previously formatted the drive as FAT instead of FAT32. I reformatted the device as FAT32, unplugged the device, plugged it back in, and suddenly it worked again as a USB 2.0 device!
Unfortunately the device failed again after a few hours, so I'm assuming it's a bad thumb drive and I'll replace it.