I was made aware of a temporary fix to the error. Just reposting it here for convenience.
Originally Posted by Aregionius
Another item that seems to help with university connections in some cases is http://www.hotspotshield.com/en
To use HSS,
1a. Turn it on and activate
1b. Open launcher, it may patch if it's the first time you've run it with Hotspot on
1c. After clicking play and BEFORE ENTERING USERNAME+PASSWORD turn off Hotspot Shield
1d. Enter your details and log in.
Now, keep in mind this fix is only temporary (hopefully). This was my response to it.
Originally Posted by TheXthDoctor
Yeah, that link worked fine. And HSS actually is getting me consistently into games.
However, I have to turn it back on before starting any games. With it on, I find it rather annoying that ads are now unnecessarily popping up in my browser. When I turn it back on after logging in, the client sometimes randomly disconnects, and in-game ping is unusually high (normally I'm anywhere from ~70 to ~110 without lag issues, but now it's around the 180-220 range which doesn't work very well consistently).
edit: Disconnection problems with HSS on so far include:
--The red disconnection message in the top left of the PVP.net client
--Extended "retrieving data from server" messages during champ select, and by extended, I mean virtually perpetual
--Permanent disconnection in game (and resulting in "Attempting to Reconnect")
edit 2: If you knew HSS could stop the firewall error, can't you figure out what about HSS is fixing the issue and then forward it to Riot to get it patched? I see no reason why I have to continue fumbling around with HSS if the problem really is this easily fixed.