Comment 1 for bug 1255771

I had the same problem after accidentally typing this:
    _name = 'complete_name'
instead of this:
    _rec_name = 'complete_name'
which of course caused a big mess in the whole database -- namely, all the M2M fields failed to work.

I couldn't fix the problem, so just restored the latest devel backup and saved my precious time.

And made myself a promise to never code while talking on the phone ;)