airplay is glitchy

i have a MacBook Pro a1211 2.16ghz intel core duo / 2GB 667 Mhz ddr2 sdram

itunes 11.1.4

Os X 10.6.8

apple tv 1 i think

i stream music from my itunes via air play to the apple tv and on certain songs mostly purchased music from the itunes store. it will randomly pause or time out for a second or two every so often. on certain songs it will glitch every 10 seconds with no music etc.

video strems flawlessly

what is the cause of this problem?