UR22 noise using amplification

Hello, I’ve just bought a new UR22. The sound is crystal clear until I turn on guitar amplification through VST (I tried both AmpliTube and Guitar Rig), at which point a very loud background noise starts. It’s not the standard distortion noise, though, it’s much much louder than normal. I’ve tried to limit it through noise gate and/or adjusting input/output gate, but I just ended up with unsatisfying results (too much noise gate cuts too many frequencies, or I end up with not enough distortion). Turning on a phazer pedal for example results in a stuttering sound, even if no note is played. And with highly distorted amplification the noise is almost unbearable.

I’ve tried on two different win8 64-bit PC in two different houses, so I’d exclude voltage/alimentation/interferences causes. I’ve tried with different cables, but please note that this background noise is present even if no guitar/cable is connected. I’ve compared the noise with another audio device (one from M-Audio) and it’s not just my imagination: the “distortion” noise is much much louder on the UR22. My vendor already gave me another UR22 to exclude the possibility of a faulty unit. I’ve even tried tinkering with sample rates and buffer size, but the noise remains exactly the same.

What could cause this problem? Could this be a driver problem, since both PCs I’ve tried it with have windows 8 64 bit version?

Oh, I’ve even installed latest 1.7.3 driver version, which incidentally states “Fixed a problem in which noise would occur during audio playback with the WDM” in the release notes… but my problem hasn’t changed a bit.

I’m kinda going crazy about this and if I don’t find a solution soon I’m afraid I’ll have to replace the UR22 with another device, probably from another manufacturer at this point…

Have you tried grounding the unit?

No, what do you mean?

Run a wire from either the UR22 casing, or PC chassis to a bonafide ground (water pipe etc.) try both variants.

Did grounding it work?