One big problem (bug?)

So, I love this game so far. One problem is, for no reason, I fail. I missed a total of two notes and got hundreds of perfects, and a great combo. Then, in the middle of a 300 combo, it stops me, and ad pops up on the bottom of the screen, and says I got an F, when the song is only 1 minute in. I dont know if this is a bug, or if it is some unknown game mechanic. And if so, it should be explained better.

twister1000000 about BEAT MP3 2.0 - Rhythm Game