Can't move vertices on model when I use alt B

For some strange reason, I sometimes cannot move any vertices with sculpting when I use alt+b to only view some of the mesh. Edit mode still works.

Grab tools, etc, don’t work. I tried applying my mirror modifier and it still does not work.

Anyone had this issue before?

Using 2.74 x64

Fixed it in a strange way. I made a new object and used the monkey. I used alt b on it, and I could still sculpt. Then I went back to my model and I used alt b on it again and now the sculpting tools worked.

I reloaded the old save and I could reproduce this each time.
Seems like a bug.

Take a look in the outliner and see if the arrow is greyed out. If it is, that is probably the problem.