I have tried the following three USB thumb drives with WARP CP 2 and all the latest drivers and fixpacks and had the following results.SanDisk Cruzer mini 512 MB - works fine.
SanDisk drive is USB 2.0 and is USB 1.1 compatible.
Lexar Jump Drive 1GB - does not work (is not recognized).
Lexar Jump Drive 512 MB - does not work (is not recognized).
The Lexar drives are USB 2.0 and I am assuming they are not backwards compatible with USB 1.1 or 1.0.