"Air gap" between a panel and the bottom of my screen.

[papillion]

Hello Everyone,

For some reason, one of my panels in XFCE seems to be 'floating' quite a bit above the bottom of my screen and is actually covering parts of applications as they run. I've tried resizing the panel (which makes it taller) but it still covers the running application. I'm attaching a screenshot so you can see what I mean. The panel at the bottom should be totally at the bottom of the screen.

Can anyone help?

Thanks!