Error when calling gtk_gl_area_make_current

I'm trying to get started with GtkGLArea. After some difficulties, I 
finally got my application to compile, but now I get an error on 
startup:



The program 'glXTest' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadMatch (invalid parameter attributes)'.
   (Details: serial 131 error_code 8 request_code 156 minor_code 5)
   (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've tried to use gdb, but to no avail, as when I say `b gdk_x_error`, 
it tells me that gdk_x_error is undefined. Another programmer thought 
that it might be a problem with the GL pixel format I'm using. I tried 
messing with it, but nothing I did seemed to help.

My code can be found here: 
http://www.nomorepasting.com/paste.php?pasteID=21883

Any help would be much appreciated.

Thanks,
Alex Diener