I did some searching and found that this problem is fairly widespread, but I wasn't able to find a solution to it.
Basically, ever since I upgraded to libxcb-1.4 yesterday, whenever I launch an application in Xorg, be that firefox, acroread, gimp, etc, I get: Xlib: extension "Generic Event Extension" missing on display ":0.0". The applications still run fine but take a long time to load. Now, I confess that I am still running xorg-server-1.5.3-r6 xorg-x11-7.2 nvidia-drivers-180.60 gentoo-sources-2.6.27-gentoo-r8 Is this because I did not upgrade to xorg-server-1,6 with the new versions of x11 libraries installed, or is that a bug in the new version of the libraries somewhere?