Why would you capo?
Anyway, did you go through the first "sticky" post in this section?
Short of that, does it happen only when you capo, or when you fret as well (should be the same)?
If its only when you capo, then you have your fix.
If both, then you probably need to level your frets first, before you decide to raise your action. Also, if you do end up raising your action (I doubt it), the right way to do it replace the saddle.