User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20100101 Firefox/21.0 (Beta/Release) Build ID: 20130511120803 Steps to reproduce: I have several files being downloaded within firefox (the actual number doesn't matter). Open history (CTRL+H). Choose a site that you visited very often and right click it. Choose "Forget whole website" (I don't have an english interface, so the entry might be similar to that, sorry! - Anyway it's the last item in the pop-up menu). Actual results: The spinner starts spinning for several minutes (5 or 6 in my case). FF does not accept any user interaction during this time. This also causes the downloads to time out, so they have to be started again afterwards. Expected results: The website should be deleted in the background, with user interaction possible in the meantime. Downloads should continue during this time.
the problem is that "Forget About This Site" tries to remove any data about that page, among that data there are the cache and plugins data, that are known to cause slowdowns. This is likely not an history bug.