I was using firefox earlier today, and it seemed to be locked up on another website, with an occasional message saying that Firefox was not responding. Down at the bottom left (I think), it said transferring data from ... (can't remember from where).
the next time I went into firefox, it said that a partial update had failed to complete, and did I want to retry. I clicked yes, and it got locked up.
I don't know if the update ever went through.
do do do do, do do do do.... Twilight zone