I can open several dozen browser tabs at sf.net concurrently loading all at once, so whatever it is, it's probably checking the user agent.
And I can start going down the list on script manager, right-clicking to update individual scripts. But as soon as I use "update all scripts", none of the SF scripts are updated. Appears that it shuts down all further operations on all parallel connections from the same IP as soon as the whatever threshold is reached, which then shuts down browser access too. After a few hours connections are allowed again.
It would be nice if we knew what the number of allowed concurrent connections was, and what timing was allowed, or any other criteria. That they would leave this sort of thing to trial and error... well, I'm no fan of SF already.
Meanwhile, maybe a couple of settings to help with this: number of concurrent connections to use, and time to wait until another connection is made.