Whenever I use Guitar Rig 5, I always hear this faint buzzing in the background which becomes more severe when the gain is turned up. I don't think it is the settings of the interface because the buzz is almost unnoticable when I am not using guitar rig but I could be wrong.
I am using a Focusrite Saffire 6 USB. I would post settings but I am unsure what ones are relevant or irrelevant.

Cheers

You can use the Gate in gtr rig, adjust the threshold till it goes away when you are not playing. (button up top for that). Also, try facing due North (play with it) to see if your direction changes the buzz or diminishes it. Might turn off your computer monitors to see if it changes. A small Buzz will exagerate when gained up, copmressed, distorted, twisted...

Yep. You need to fiddle with the gate button. Just like a real amp the more distortion/effects you put on the signal the more hum/feedback/general noise you get. There is a feature where you turn your guitar and interface up to recording level but don't play anything (dampen the strings with your hands) then when you are sure it's at the quietest your signal will be you merely click the Gate knob and it auto adjusts to cut out all the noise. This way it just BARELY applies the gate up to the point it is need but as soon as you play the gate opens up. This however used to work quite well for me but for some reason stopped so I just adjust the knob the old fashioned way. Just get the signal to it's most idle at levels you want to record at then adjust the knob until the hum and noise just barely disappears.

Are you playing with single coil pickups through it? When I play my Telecaster through some of the very high gain presets the buzzing is ridiculous. They work better with humbuckers. 

I have the same probleme i have 2 humbuckers and when i record my sound to high or to low wnen a finish project

These guys are right about pickups. It also depends as well on your location. My studio is in the basement with my home's circuit breaker panel box on the other side of the outside wall. Certain pickups and mics are very prone to RF EM fields in their location.  I have a SURE SM7B that I use for voiceovers that works fine, but I also have an EV RE20 that buzzes like crazy depending on where I am in the room. The difference is that that SURE has shielding around the capsule that the RE20 doesn't. Same applies to guitar pickups. Even proximity to your PC monitor can cause problems.
 

Does the buzzing go away when you touch your strings?

Buzzes that go away when the strings are touched doesn't necessarily indicate a problem. I've an SG that buzzes and picks up wifi frequencies from the router and it's string and other earthing is fine.

Any guitar will buzz/pick up EMF if there's enough electronic noise about. Computers are electronically noisy, domestic light dimmers, routers, phones, transformer or switching power supply plugs, all make lots of noise. Humbuckers are supposed to cancel noise but are rarely 100% effective, and the more gain or compression is added to the guitar signal the louder the noise gets. Even a short guitar lead can act like an aerial and noise enter the system that way,

Sometimes simply facing in a different direction makes a big difference, or getting a few feet further away from the source of the electronic noise.

Many of the high gain presets for Guitar Rig are noisy at low signal.
There is a Noise Gate rotary knob up at the top of the interface that you can adjust to get rid of that noise.
Most of the cleaner presets should not be noisy. Might be as simple as the software mimicking what an analogue fx chain would do.

I have alot of issues with single coil pickups especially seated so close to my computer monitors. Step away 5 feet no noise, tilt the guitar away from the monitor, no noise.
 
 

tlw
Buzzes that go away when the strings are touched doesn't necessarily indicate a problem. I've an SG that buzzes and picks up wifi frequencies from the router and it's string and other earthing is fine.

Any guitar will buzz/pick up EMF if there's enough electronic noise about. Computers are electronically noisy, domestic light dimmers, routers, phones, transformer or switching power supply plugs, all make lots of noise. Humbuckers are supposed to cancel noise but are rarely 100% effective, and the more gain or compression is added to the guitar signal the louder the noise gets. Even a short guitar lead can act like an aerial and noise enter the system that way,

Sometimes simply facing in a different direction makes a big difference, or getting a few feet further away from the source of the electronic noise.

No, noise that goes away by touching the strings doesn't always indicate a problem with the guitar, but if it does go away touching the strings, it rules the software out as the source of the problem.