Getting a sour note

This is my first time to post so please be gentle with me! I have a Squier Strat electric and am having a problem with a sour note. I have the open G tuned correctly but when I play the A at the second fret it sounds really flat. So when I play a D, Dm or something like that it sounds off.

My main question is: Do I just need to replace that string or is there possibly another problem.

Any help would be greatly appreciated!

Eric :D

Sounds like the intonation needs to be adjusted. With a tuner, check the tuning on the G string (I love that) and then fret the G string on the 12th fret and check the tuning. If it's not in tune on the 12th fret, the intonation needs to be adjusted. Adjusting the intonation involves moving the saddles on the bridge back and forth, depending on whether the fretted note is flat or sharp.

you could try changing the string (strings maybe) anyway. old strings send the intonation out too, but its probably what jfrick said ;)

Thanks, JFRICK that did the trick. It just needed a little tightening and now it sounds fine.

Eric :D