Do you have any custom material you've created?
I had several errors pop up. They were between the new Unearthed Arcana feats added in 1.5 and my files for the same thing. Then I remembered that I had uploaded them to the GIT site for inclusion in 1.5.
I just did a quick check of the .user files and can't find any file called 5eExtras.user. Is this a personal .user file?