windows movie maker help

hi ladies..i could use some help

I made my daughters 1st bday montage on WMM with no trouble. easy peasy.

almost done with her 2nd bday montage and now all of a sudden two of the four songs I have won't play. It's odd b/c two are from the same album! Even weirder is that at one point it was working just fine.

I'm soo close to being done - I don't want to bail on it now..

Anyone have any tips or suggestions? I'm going batty!!