What in the world does this mean? It does it at least once a day now...

 

likely a bad shift fork

 

A Google search brought up a lot of people saying this a sign of a bad transmission.

 

that's a little vague, surely the entire transmission isn't bad.

 

It's the bottom line because, in the end, it appears that you need to replace the transmission, unless you have the expertise or patience to pull your tranny apart. I read one post that also pointed to a bad shift fork, but most threads seemed to conclude that the problem is related to worn synchros.