firefox slowness -- X server problem?

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

Since I've updated to a 20100802 snapshot of -current (from 20100712
or 20100721, I forget), firefox has been behaving very laggy.

On an unloaded machine with lots of RAM, firefox sometimes needs ten
seconds to switch from one already loaded tab to the next. It seems to
be worse for pages with pictures and better if there's only text.

tnn@ is not seeing this; I think he's using X from pkgsrc while I'm
using X from base. I have an ATI Radeon X300, using the radeon driver.
I've also tried wip/firefox (firefox 4 snapshot) but it's similar
there.

Also, ALT-Tab between two open xterms takes noticable time (up to two
seconds). That's the reason I suspect it might be a X server problem.

Has anyone else noticed similar problems?
 Thomas