Any flash plugin will cause an immediate galeon exit from an X11 error : > galeon --sync --disable-crash-dialog http://www.youtube.com/ The program 'galeon' received an X Window System error. This probably reflects a bug in the program. The error was 'BadMatch (invalid parameter attributes)'. (Details: serial 120 error_code 8 request_code 146 minor_code 3) (Note to programmers: normally, X errors are reported asynchronously; that is, you will receive the error a while after causing it. To debug your program, run it with the --sync command line option to change this behavior. You can then get a meaningful backtrace from your debugger if you break on the gdk_x_error() function.) I talked to Philip Langdale, but he had no immediate suggestions. Since the flash plugin works fine with both Firefox and Epiphany, I suspect something is wrong either with the way galeon is build (against firefox-devel), or possibly some environment problem makes the plugin unhappy...
Some more information here: https://launchpad.net/distros/ubuntu/+source/firefox/+bug/23392 Added g_setenv to galeon source code to fix this issue.