USB devices

[Chris]

Could somebody please explain how USB devices "attach" to the hardware.

My problem is I know that the Epson CX-5400 is supported by SANE.

It gets ulpt0 assigned to it and printing using CUPS is great. 
Unfortunately SANE needs uscanner to also attach to this USB device in 
order for it to scan.

My Epson 1260 worked fine prior to this.

Any documentation and/or help would be appreciated.

Chris