I am using Arch (x86_64). I just installed xfce4 and xfce4-goodies via pacman for the third or fourth time (because I've uninstalled and reinstalled in hopes that this bug goes away, but no luck yet).
As root, the xfce4-panel seems to work okay. As a user, the panel always starts up with the "Welcome to the first start of the panel" window.
When I click "Use default config" the panel does not work. When I click "One empty panel" it does, but after I logout and login again, this window reappears.
When attempting to start xfce4-panel from terminal while l am logged in as a user, I see the panel flash on and off at the top of my screen, but it does not run. When I do this, the terminal reads:
(xfce4-panel:4332): GLiB-GIO-CRITICAL **: g_file_new_for_path: assertion 'path ! = NULL' failed
(xfce4-panel:4332): liblauncher-CRITICAL **: launcher.c:516 (launcher_plugin_item_duplicate: expression 'G_IS_FILE (dst_file)' failed.
(wrapper:4333): Gdk-WARNING **: GdkWindow 0x2200004 unexpectedly destroyed
The program 'wrapper' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadWindow (invalid Window parameter)'.
(Details: serial 224 error_code 3 request_code 18 minor_code 0)