raybob would be of better help, but review this forum post first:
http://www.rejetto.com/forum/fhfs/way-to-change-default-url-root/msg1059177/#msg1059177
since you've stated that you have fhfs on a separate drive,
i'm almost willing to bet that you didn't specify the users to be on that drive(so it is defaulting to "c:///etc...") and/or that drive path that you have set was not set to be the same drive letter at each usb insertion/startup...
http://www.rejetto.com/forum/fhfs/way-to-change-default-url-root/msg1059177/#msg1059177
since you've stated that you have fhfs on a separate drive,
i'm almost willing to bet that you didn't specify the users to be on that drive(so it is defaulting to "c:///etc...") and/or that drive path that you have set was not set to be the same drive letter at each usb insertion/startup...