PS2 won't boot and no sound during start up

[Replicatorz]

I have a Messiah chipped V4 PS2, which has worked well for the past 3 months since I modified it.
But now during the start up screen, where you see the multi coloured atoms moving around the screen there is no sound, and all of the disks I insert cause the PS2 to go to the browser screen,select between the memory card and disk, and won't boot from there.

Any Ideas

Cheers