Usually the easiest way to debug a program is to run it from a console to see any messages that display in stdout.
I'm not a Gnome user - so I can't tell you what the panel binary is, but I'm sure a quick bit of detective work with google and ps you'll be able to work it out. (kill the panel, then start it again from a console. stdout should log a clear text output to the console you started it from and give you some hints as to why it's not working)