What could be the reason that vertex paint wouldnt work?


I wasnt sure where to post this question.

I can open a new file, add a cube and vertex paint it, easy.

But in a file I have been working on for a while I am unable to vertex paint the object.

Yet before I could not delete the vertex painted image from memory, now I cant get one to paint?

LOL, very odd.

I just opened the file without the ui and got it to work…but I wonder how this happens?

No clues?..