fps dropping down as I play since the 3/27 patch

[Kundry.1249]

I'm having fps problems after the patch.

 

More specifically: when I first start the game, it's fine, I get around 40-50 fps. But as I play the game (fractals, pvp, just sitting in Lion's Arch, it doesn't matter), fps keeps dropping down until I reach around 10 fps in 10-20 minutes. The funny thing is, if I tab out and touch my battery settings (I'm on a laptop), it goes back up to 40 fps, from which point it starts dropping down again. I don't actually have to _change_ the battery settings: I can just change it from medium high to high back to medium high, or from high to medium high back to high and it will work.

 

Anyone know what is going on?