What does "Preparing Security Options" mean when trying to use "End Task"?

Today the browser was very VERY slow and crashed continually (grrrr). It was very difficult to get "End Task" to function at all, and each time this was tried, the screen read "Preparing Security Options".

Also, "End Task" did not function normally. I had to right click somewhere and then select a way to actually shut down the browser.

Any info and/or advice appreciated.