I have noticed in my exploits that the progress-bar doesn't always work when in the "Compressing Quicktime" stage of the export, but the movie always gets exported.
It can take quite some time, especially if the file-size is very large (think about how long it takes to simply write the file to the drive, let alone compress it in memory and then write it to the drive). On my machine (a hyperthreaded P4 with 1.5 GB RAM) it can take upwards of 30 mins to output a 1GB video file, and even longer for a larger file.
If you are still able to cancel it, it is likely that the export is proceeding as normal, just not reporting it properly. I say let it sit for a while and see if it finishes.
Another way you can see this, typically, is to browse to the file on the computer and watch the file size. If it is growing, the export is running. It is just a matter of time until it finishes.
Cheers for the reply Ross.
I'll leave the scene test to export over night and I'll let you know tomorrow how it goes.