Is My Soundcard Dying?

I think there's a problem with my soundcard. I just received these wonderful Sennheiser PC 360 headphones, but when I jack them into my soundcard, there's some tiny cracks in the sound and it is as if there's more sound coming out of the right channel than the left. And I can't hear anything wrong when they're jacked into my mobo.

I also recently had a problem with it (other headphones though) where it would make a lot of white noise when there was a mic plugged into it. It all disappeared when I moved the mic to the mobo's mic output.

The soundcard IS 3 years old, so could this be the last breath from it?

It could be a power noise problem. I've had problems with crackling in cheap USB powered speakers whenever I moved my mouse.

But I've never noticed it before?

EDIT: I'm aware of the problem of background electronic noise in PC's, and I've also encountered that previously but as a white background noise, not a crackling sound.

A little google searching suggests checking the PCI latency by using this tool.

http://downloads.guru3d.com/download.php?det=951

It suggests making sure all devices get an equal share of the latency. Make sure you update the audio drivers.