Detecting USB drive at boot

I setup a 100meg persistent home on my memorex traveldrive, everything seemed to go fine. Problem is that when I restart, sometimes knoppix will tell me that it has detected a persistent home on the drive and sometimes it won't detect it. If I use the command 'knoppix home=/mnt/sda1' at startup it will sometimes find my home and sometimes it won't. Any ideas on why this could be happening? The USB drive works fine, I can access it in either windows or linux.

I'm running a Dell Inspiron 8200, which only supports USB 1.1, it has the latest bios version.