simulator_gazebo/gazebo/scripts/gui (core dumped)

edit

I don't know what the optirun command does to set the DISPLAY env variable.. but on my machine, when I don't set the DISPLAY variable to something useful I get the message

X Error of failed request:  BadMatch (invalid parameter attributes)
  Major opcode of failed request:  146 (GLX)
  Minor opcode of failed request:  5 (X_GLXMakeCurrent)
  Serial number of failed request:  22
  Current serial number in output stream:  22
Segmentation fault (core dumped)

for reference, your error messages was slightly different from mine..

X Error of failed request:  BadMatch (invalid parameter attributes)
  Major opcode of failed request:  72 (X_PutImage)
  Serial number of failed request:  38
  Current serial number in output stream:  40
Error [Transport.cc:102] Unable to get topic namespaces in [50] tries.
Error [Node.cc:68] No namespace found

To fix my problem, I run xvfb (can be run in the background or in another terminal)

Xvfb :1 -screen 0 1024x768x24

and then run gazebo

DISPLAY=:1 rosrun gazebo gazebo my.world

If there was a display already open on the machine that I had access to (e.g. if I was physically logged in through a GUI or something), I could have also set the variable to that value as well.