The problem#
I recently replaced my old Nvidia graphics card with a newer one.
Upon booting up, I ran glxgears to test that 3D graphics
were working properly and got an error like
X Error of failed request: BadWindow (invalid Window parameter)
Major opcode of failed request: 155 (NV-GLX)
Minor opcode of failed request: 4 ()
Resource id in failed request: 0x1200003
Serial number of failed request: 34
Current serial number in output stream: 34
The solution#
Either delete /etc/X11/xorg.conf or edit it and remove (or
comment out) the "Files" section; that is, the lines
Section "Files"
...
EndSection