Buffering problems for Samsung LED 6050

I recently upgraded my internet speed from 6mg to 24mg. While I had the slower internet I had an old linksys router (WRT54GS V2) and a basic modem that was provided by my ISP. I was able to use Serviio perfect. However, now that I'm on a new Motorola Wireless Cable Modem (SBG6580) i have run into problems. When I try to watch a movie or play a MP3 I am constantly having to wait for it to buffer every 15 seconds to the point where I cant even use it. Any Ideas?