I think the only limitation to the render length is the available space on your HD. I ahve rendered 3 hours of SD DV but I rendered to Main Concept Mpeg2 and AC3 so that I could burn it on a DL DVD. Worked fine
So you have 1:04:23 on the time line? Does the time line play all the way to the end? Are you rendering to MPeg2 DVDA compatable Main Concept? and a separate AC3 audio render? When you take that rendered Mpeg2 file and play it with a player on the PC does it play all the way through?