Microsoft Movie Maker Not Centering Video on Preview Screen
Sorry this is a little late but but did you ever figure it out? I wouldn't recommend using windows movie maker for much of anything. The reason it doesn't accept .mov files is because it's windows movie maker, a Microsoft product using microsoft proprietary files .AVI and .WMV... .MOV is quicktime which is Apple. 

You mentioned that you converted over 2000MB of files over an extremely slow internet connection so I'm assuming you didn't use software on your machine. I would start by blaming the converted file. It could possibly be that  movie maker can see the file but once you start adding effects everything goes to crap. 

windows movie maker has saved me in a last minute pinch when I needed to fix something for a powerpoint presentation and didn't have my studio with me, but other than that I would say purchase the correct software, hire a a pro, or don't take on 2 hour deadlines when you don't have the proper equipment.