Found the problem. Checked Apple System Profiler with the flash drive plugged into a USB port, and found the drive listed with the other USB devices, so obviously the system was recognizing the drive, just not placing it on the desktop. Checked the Driver Name, and found that it was not the correct one (Mass Storage Driver). Apparently installing my Firewire external drive had also installed USB extensions, which I don't need. Turned those off, restarted, and travel drive appeared on the desktop. So it was a simple extension conflict. Thanks to those who looked at/replied to this entry. Maybe this will help someone else.