Xvfb freezes initializing GLX extension

问题:

I am trying to run a headless Xvfb server to capture screenshots on Amazon EC2 micro. But it is getting stuck at GLX. I installed GLX, Xvfb and all the libraries using this script: https://gist.github.com/joekiller/4144838

DISPLAY=:1 firefox http://www.google.com &

Here is the console output

Xvfb :77 -screen 0 1024x768x24&
[7] 29462
[ec2-user$ Initializing built-in extension Generic Event Extension
Initializing built-in extension SHAPE
Initializing built-in extension MIT-SHM
Initializing built-in extension XInputExtension
Initializing built-in extension XTEST
Initializing built-in extension BIG-REQUESTS
Initializing built-in extension SYNC
Initializing built-in extension XKEYBOARD
Initializing built-in extension XC-MISC
Initializing built-in extension SECURITY
Initializing built-in extension XINERAMA
Initializing built-in extension XFIXES
Initializing built-in extension RENDER
Initializing built-in extension RANDR
Initializing built-in extension COMPOSITE
Initializing built-in extension DAMAGE
Initializing built-in extension MIT-SCREEN-SAVER
Initializing built-in extension DOUBLE-BUFFER
Initializing built-in extension RECORD
Initializing built-in extension DPMS
Initializing built-in extension Present
Initializing built-in extension X-Resource
Initializing built-in extension XVideo
Initializing built-in extension XVideo-MotionCompensation
Initializing built-in extension SELinux
Initializing built-in extension GLX

How to fix? Is it common for xvfb to be so slow in ec2?