By export do you mean export the objects or the whole scene.

Okay I am guessing you have set up batch render correctly using render globals with Frame/Animation Ext on something like name#.ext and with a start frame of 1 to End from of N with frame padding of whatever.

I have never had this problem myself,

I have had trouble even recreating this problem as a start frame and end frame of 0 still gives you a rendering complete & mayaRenderLog.txt . The only thing I can suggest is save your scene reinstall maya and try again maybe maya has just thrown a wobbly I know my mental ray has done that before just up and decided it didn't want to work anymore.

What version of maya are you using has it had any other probs.