logout not always works

[bsh]

Ok, i'd like to report this as a possible "bug" (nothing serious though)
I am not quite sure if this is "xfce4" or "xfce-panel-menu-plugin" or even "xfce-session" or something else, sorry.

I have two pc's in a very similar scenario, both having this issue.

The scenario: file server on a small network of windows pcs. the server runs ubuntu 7.04 (feisty). the server is "headless", i use ssh or vnc to do maintenance. the window manager is xfce4 (from the ubuntu repos), but since it's plaing ubuntu install (not xubuntu!), it came with gnome as default, but i use xfce.
When i log in to the gui using VNC, then i want to log out, i click the "xfce menu" button (the one similar to the start menu in windows xp), then select logout.
This then fades the desktop and pops up the logout dialog, where i can choose from logout, user switch, shutdown, restart.

However, this does not always happen!
Sometimes when i click the logout in the menu, it does nothing, just puts me back on the desktop, and doesn't always display the logout dialog.
Sometimes i have to try it 4-5 times until it displays the popup.

After that, it logs out/reboots/shuts down as normal.

I don't know which plugin does this. And since i use VNC, i can not tell if it happens with a physical login too, i have never tried. Maybe it only happens in a VNC session? Dunno.

And as said, I have 2 such servers (one at work and one at home), both are ubuntu 7.04 with xfce, both headless, both with VNC, and this happens on both of them, randomly.