X11: X Error of failed request: BadAccess

Using X11, with forwarding enabled, I have have had problems opening mozilla and firefox and keeping it open. Shortly after opening the window, it will spontaneously close, leaving the following error message in my terminal:

X Error of failed request: BadAccess (attempt to access private resource
denied)
Major opcode of failed request: 102 (X_ChangeKeyboardControl)
Serial number of failed request: 5952
Current serial number in output stream: 5961