At the risk of stating the obvious, that sounds like the hard drive you're trying to render to is full or almost full. Did you check to see if there's enough space for your render on that drive? Depending on the codec you choose and the length of the comp you're trying to render, the file size could be huge and it might not fit on your hard drive even if it looks like you have enough space. If you're render is stopping in the middle, that could be the reason why. How much space is on the drive you're trying to render to and what are your render settings? Maybe a screenshot of the following info as it shows up in your Render Queue would be useful:
Also, let us know how much space is on your OS disk. You need some space on that drive while transitioning.
Oooh, I see another potential problem.
Does this comp contain video? If so, you need to double-check the frame rate of your footage. Chances are good that your comp's frame rate needs to be 23.976, and not 24.
The reason: when shooting 24p, most readily-available cameras shoot at 23.976 and not 24. Sure, there are cameras that DO shoot 24, but you have to check.
No video in the comp? The question then becomes, "How are you delivering it?" If you intend to integrate animated graphics with video, the frame rates have to match.