Off-taste after kegging

Hi, I kegged my beer for the first time 3 weeks ago. I force carbonated and it tasted great until yesterday I started getting an off flavor. I'm having trouble describing it, but it almost tastes like maybe too much carbonation, but my porter does not have too much foam, doesn't gush, etc... has anyone else had this problem, it may not be a carbonation problem...

 

If it's overcarbed, you'll notice a slightly bitter quality to it. What was your temp and psi?

After 3 weeks on CO2, if you don't have foam (assuming you don't have leaks) then it's because of reasons other than no carbonation.

 

I've got it set to 10psi and it holds at 40 with a 3 degree differential...I'll taste it this afternoon to see if it's a bitter taste I'm getting

 

It certainly shouldn't be overcarbed at 10psi/40 degrees. That's only about 2.3 volumes of CO2.

 

Is that what it's set at, or what you carbed at? Some people crank pressure way up for days then drop to "serving" psi. Also do your beer lines have bubbles or air gaps in them?