hi,
for 6 years i've been running an RPM at home with an offline PC (windows XP).  it never even travels.  i was surprised a few days ago to find the noise levels for inputs 1/2 & 3/4 peaking at -30db when set to phono 0db.  the noise remains even with nothing connected to the RPM.  usually that value would be closer to -80db.  the noise on line level input is also higher than normal.  it's easily audible through the headphones (constant mid-frequency tone).  i'm now also hearing a quiet low frequency "pop" sound when i power up the laptop with my amplifier on (wondering if it's related).  another thing i've noticed recently is that switching between line/phono sensitivities causes big spikes of noise (bigger than normal - clipping sometimes).

jiggling either the I/O box itself or the power supply anywhere near the I/O box increases the noise level.  on the headphones this movement sounds like a low-frequency rumble.  moving the firewire cable has no effect.

the power supply is cosmetically perfect and all my other gear powered by the same power bar is working fine.

thanks in advance!