PS2 Problem

[koalabear1]

I have a PS2 with a NEO4 installed. It had been working perfectly for the past 6 months, but all of a sudden things arent going so well. Whats happening is when I turn it on, it gets to the blue browser screen but wont actually load any disc at all. Ive tried PS2 originals, copies, dvds and music cds with no luck. I can hear the disc trying to spin, but it doesnt load. Ive opened up the PS2 to check if any of the NEO4 wiring had come loose, but that all looks fine. Has anybody come across this problem and know what the fix may be. Could it be a fuse on the main board or a laser prob??
Thanks for your help.