Exporting

Hey, 

I'm having issues with exporting a video from Premiere Pro. When I export the video a message says that the video couldn't export properly and try to open the finished video it comes up with a message saying it can't be opened. I'm working on a Mac (Laptop) and I'm exporting it to my USB. The video is 2.5hrs long and I made sure all the settings were correct but it just won't work. Is there something I'm doing wrong. Would it be better to just upload it straight to YouTube (I just want to watch the finished video on the TV)