USB 2.0 DVD Burner error

I have a DD0201 Optorite DVD+/-R burner. I recently bought an usb 2.0
external enclosure to go with this drive. The computer I am connecting
it to recognizes the drive fine, but the drive will freeze or error out
about 10% into the process of reading or writing a dvd or cd. The drive
works fine when connected to the ide cable. The problem occurs when it
is connected to the usb 2.0 external enclosure. I installed the latest
firmware (2.60E) and I'm running a P4 2.0Ghz with 1GB of RAM with
Windows XP. Does anyone have any suggestions on what I can do or what
I'm doing wrong?