I have a Peavey BXP Grind 4 string. The action on it seems a tiny bit high, but my main concern are the A and D strings. At higher frets, basically anything past 12, i get fret buzzing, to the point that a note isn't even heard. However, the E and G string both sound prefect at the higher frets, its really weird. Any help?
Check out the FAQ and www.tunemybass.com on how to perform a setup.

Here's my usual advice. If after reading both of those, the process doesn't make sense, take it to a reputable shop and have them do it for you. Better yet, get them to demonstrate to you how to do it. Its not hard, but can be daunting the first time you attempt it.
yup yup, take it to a shop watch them do it for you. The FAQ's are wonderful information-wise, but if your a visual learner and cant quite get it, watching someone do it makes life so much better