I'm also having this problem. It usually only lasts a few minutes but while it happens it's just nigh-unplayable. Worked fine before the graves patch.

I am also having this problem,all games,all the time.
HD 5770 1gb

They're at blizzcon XD

Been testing this with friends to verify claims that this is only happening on Summoner's Rift. Currently, we've been doing some Dominion to test if it occurs upon that map, but it doesn't seem to be a case that Crystal Scar causes the same FPS issues. Since this came immediately with the Graves patch, I think it is likely that the issue is located within the Summoner's Rift - Harrowing map.

Can anybody confirm this, potentially by testing on Twisted Treeline or other Summoner's Rift maps to see if the same FPS loss happens?

Note that this is specific to the issue of FPS loss following the Graves patch, not the other FPS issues starting 3-4 patches back.

Could Be Processor

it's not ur hardware guys, it's the patch. if you noticed, it starts spiking when the caster minion starts attacking. Anyhow I started a thread in bug section ...
http://na.leagueoflegends.com/board/...1391213&page=2

I think my problem is sort of similar...
My game decides to freeze (not majorly, but enough to be really annoying, like 1-2 seconds) at select points during the game:
-When an ally/enemy has been slain (or when the announcer says "Thirty Seconds until minions spawn!). This is the most annoying one.
-The first time I last-hit a minion.
-When I die/am about to be killed (alive pre-freeze, dead post-freeze).

It makes it really hard to play the game decently. Please help!