iphone 3G build-in ipod problem

First time buy an iphone. I love GTA series, in fact I converted GTA: Vice City's in-game radio station into one single mp3 file (those 80's music is classic). After I transfer them to my iphone 3G, when I play the mp3 (60 mins long), sometime sound skips for a couple seconds. The weird part is that because it is a "radio station", the sound skipping only happens when the "radio host" is talking, but when there's song playing, no sound skips.

Is this a firmware problem? Or is it something wrong with the mp3 file? How can I fix it?

That sucks. Even my cheap $20 mp3 can play long single files. I'm gonna report this to Mac. Some of my downloaded podcast (usually 1hour long) start to skip as well. Mac really needs to improve their firmware