Check out my comments on the "Bugs" discussion thread. I've been having this problem for MONTHS. It's very, very frustrating and time consuming, and there seems to be no rhyme nor reason for it.
Tell BL. I can see comments, btw, but they're planning on updating things on Tuesday, so let them know about this, too, so they know to fix this, as well.
I used to have that problem, but only on a specific web browser. I eventually ended up uninstalling the web browser and re-installing it (instead of just updating). That solved the problem.
Thank you!