I got the same problem! I tried reinstalling and it DID work but then when i close the technic launcher and start it up again it doesen't work... This is the error report when opening it with a terminal:
may 22, 2013 5:56:47 PM org.spoutcraft.launcher.entrypoint.Start launch
INFO: Args: []
The program 'java' received an X Window System error.
This probably reflects a bug in the program.
The error was 'RenderBadPicture (invalid Picture parameter)'.
(Details: serial 255 error_code 163 request_code 149 minor_code 6)
(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.)