wont play dvd-rw

Hi there i tried burning a load of mpegs to a dvd today, using Cucusoft avi to vcd/dvd/mpeg creator pro i burned 1 clip to a dvd just to see if it worked and it did work. So i tried burning a second disc with lots of files on this one and it wont play, it just comes up as a blank disc,

When i used the software it had 2 'modes' batch and merge, i used merge thinking this would merge them all it to one file. I thought it worked cuz it went through a lenthy conversion stage then the burn stage with no errors or anything.

Does this mean you can only put 1 file on each disc?

Or is it that i need to merge the files seperatley before burning them as one file?

thanks for you time.

Adey