The only topic I could find with a similar problem going on was this one, but that’s more about symptoms than causes… however, there are a good number of links going from and to the UI freeze topic, and I did not check all of them. If I remember it, I probably posted in it, and if I posted in it, I probably linked there, so that would be a good place to start.
All the same, this report could perhaps be merged with the UI freeze one, as in this case at least it was that cause.