Scrolling pages fast in browser (holding down space to do it) causes system hang (sometimes shows corruption in screen after hang).

Gentoo ~amd64
X.Org X Server 1.5.2
Mesa 7.2
xf86-video-intel-2.5.0
[snip]
(==) intel(0): Default visual is TrueColor
(II) intel(0): Integrated Graphics Chipset: Intel(R) 945GM
(--) intel(0): Chipset: "945GM"
(--) intel(0): Linear framebuffer at 0xD0000000
(--) intel(0): IO registers at addr 0xEE100000
(WW) intel(0): libpciaccess reported 0 rom size, guessing 64kB
(==) intel(0): Using EXA for acceleration
[/snip]

Xorg.log doesn't seem to be showing anything except:
[snip]
(WW) intel(0): PRB0_CTL (0x0001f001) indicates ring buffer enabled
(WW) intel(0): Existing errors found in hardware state.
(II) intel(0): using SSC reference clock of 100 MHz
(II) intel(0): Selecting standard 18 bit TMDS pixel format.
(II) intel(0): Output configuration:
(II) intel(0):   Pipe A is off
(II) intel(0):   Display plane A is now disabled and connected to pipe A.
(II) intel(0):   Pipe B is on
(II) intel(0):   Display plane B is now enabled and connected to pipe B.
(II) intel(0):   Output VGA is connected to pipe none
(II) intel(0):   Output LVDS is connected to pipe B
(II) ThinkPad Extra Buttons: Device reopened after 1 attempts.
(II) TPPS/2 IBM TrackPoint: Device reopened after 1 attempts.
(II) AT Translated Set 2 keyboard: Device reopened after 1 attempts.
(II) Video Bus: Device reopened after 1 attempts.
(II) Video Bus: Device reopened after 1 attempts.
(II) intel(0): EDID vendor "LEN", prod id 16384
(II) intel(0): Printing DDC gathered Modelines:
[/snip]