Noise on Stereo Outs when USB connected

Hi All, It sounds like I have the same issue here.
Mac computer with Logic 9 and virus Ti sw version 5.0.3.00.
When i start up the VST virus plugin I have a constant noise.
Any one can help?

Is the Virus your soundcard as well?
Check if your "INPUT THRU" parameter is set to more than 0.

Hope this helps.

Hi Flabberbob thanks for the replay.
No I am not using it as Soundcard, but even if I do it gives the same problem.
If I just remove the Virus plugin in Logic the Noise disappear so I can't understand if it's a sync problem or what.
I have updated everything and also done a factory reset with no success.
I can't find the INPUT THRU parameter

INPUT THRU is one of the input parameters in the LCD menu (p.90 in the reference manual). set it and/or the input boost to 0.
Sync problems sound like crackle and dropouts only while the track is playing. Does it sound like that or more like constant hiss?

Ok found it thanks. It is set to 0.
as soon as I start the plug in what I hear is just a constant noise (almost like white noise) and no matter what I do, play, stop or something else and nothing change. if I play some notes I see the meter bar in the VST Virus plug in moving like if it's correctly playing but in the meter bar of Logic channel I can see this constant noise playing (and hear it too).
I tried changing USB port, removing all other USB devices but nothing.
Some Logic Settings?
I am still using Logic 9.1.8 32bit.

Hi all I thought that making a video of it could have helped understanding the problem i have. Here is the link:
https://www.youtube.com/watch?v=dH9EBz7KZ5w
thanks for helping

I had the same problem which was solved using a Olimex USB isolator. The casing looks a bit amateur but it works a treat.