Definitely sounds like an intonation problem. Before you back over your guitar in the driveway (lovely imagery with that one :-), you might try putting a fresh set of strings on the guitar. Back when I was a teenager and didn't have money to change strings often, I would build up all sorts of crud and corrosion on my strings. Even with removing the crud on a regular basis, eventually my guitar's intonation would be off. I sweat a lot and my sweat was really corrosive to metal, so if I go too long between string changes, my intonation goes off.

I've also read in the guitar tech forum here that, though rare, you can have a bum string out of a fresh pack that can throw off your intonation.

Something else to look for - you mention that at the 8th fret is where you see the problem. Does you neck dip at that point? If your action is really high at the 8th fret, your intonation can seem off since you add tension to the string bringing it down to the fretboard. If that was the case, it would most likely effect all 6 strings, not just the high E.