I believe this is related to the battery icon which is controlled by the xfce4 power manager. When I set the power manager to never show the icon...I do not get the extra space added after every suspend (on a freshly installed and updated Lubuntu 11.10 eeepc 1005ha).
Try this. First get rid of the extra space (if any) by resetting the panel.
Then open the XFCE Power Manager.
Under 'System tray icon' select 'Never show icon' and click Close.
Now try suspending the computer and see if that fixes it.