The most likely cause is a rogue clip down the timeline. I've replied in your other discussion how you might track it down.
Insanity is hereditary, you get it from your children
One way is to press the \ key (above the Enter key). This will show your entire timeline.
If the light gray Work Area Bar (along the timeline's "ticker" ) is stretched beyond the end of your movie (in your case, it will likely be over 2 hours long) then you have some rogue clips floating around out there.
Click and drag your mouse over the area to select them and then press Delete.
When you've got them all, the Work Area Bar should shrink to the size of your actual movie.