Well It's not definitive - The Clutch release bearing i have known to:
1) Make a noise - then quiten with the pedal depressed
2) Be quiet but only make a noise when the clutch is depressed !!

But if the noise totally goes away with the pedal down then i would say it's more likely to be the release bearing than anything else !!

Did you fit a new clutch KIT when you had the gearbox done 2k or so ago ?? - ie a release bearing fitted ??