Long freeze-ups when tabbing back to client

[Noselacri]

If I alt-tab away from EQ (in windowed mode) and back, I get a really long freeze-up, like 10 seconds. I also get them randomly while playing, for no visible reason. Just got back from a couple of months of not touching the game and it never happened before, but I have done nothing, am still on the same computer, playing from the same install. What could be causing this?