I know this is an old post.. but I just read it while searching for a similiar issue.. and I think you’re problem may have to do with your photos..
I had a similiar problem when I added phots. But, I realized each photo was about 8 meg.
To resolve this, I used a program (in this case lightroom, but that shouldn’t make a difference) to reduce the files dramatically (largest file I think is now 2 meg) and it appears to be working smoothly.
You shouldn’t lose much quality as you’re likely not trying to blow each photo up.
Edit photos outside of vegas and then save to 1-2 meg per file (or less) and you may be fine.
Dave