imacon precision II scanner problem

hello to all! i have a precision II that has started making all white
scans. the book says check the bulb, but it's ok. did this once
before, but healed itself. the preview is white, the scan is white,
the lighttable and scan bulbs are good, the mechanism is working.

i use mac g4, flexcolor 4.0.2; all this had been working.

btw, the software won't see the scanner unless i turn on the scanner
before starting the computer.

thanks for any any ideas.

bz