[client] lol launcher hanging as if frozen

Ever since the patch--not the most recent Tristana patch, but the only immediately before it--every time I launch LoL, after I sign in and first arrive on the main LoL screen, the program hangs as though frozen.

If I try to touch the client, it greys out, and Windows even gives the message "this program is not responding, blah blah blah." This happens literally every single time.

I've also seen it happen on the sign in screen, but only quite occasionally.

After a random amount of time that is usually less than one minute, the program starts running as usual--even if the Windows message has come up--and from there on everything runs fine. Again, upon launching, the program appears to hang as if frozen, and after about a minute starts running normally; this has happened literally every single time since the patch before the Tristana patch.