If you have a 15Gig m2v video, it must be around 8 hours since 2 hours of DVD video is around 4 Gig. If you can, try exporting (from Premiere) each seperate sequence as an avi file. Let Encore transcode the files. If you can export 1 big sequence you should be able to export a bunch of smaller ones.
Encore is a DVD authoring application. It was not intended (ever) to be used as an editing or production tool. Its a Post Production tool. Your video files are supposed to be ready for delivery by the time Encore sees them. Using Encore as an editor is only asking for problems. The biggest being the audio and video sync. Guaranteed to lose sync every time.
Honestly, its best to figure out why your having problems exporting from Premiere because Encore will introduce new problems. The problem your experiencing now is just the beginning if you can't solve your Premiere export issue.
I can't help you on that because I don't know what version of Premiere your using, and what your settings are.