Xubuntu top panel randomly reverting to default Xfce appearance

[nairanvac]

I logged in just a minute ago, and it appears that the top panel on my Xubuntu desktop has defaulted to the plain Xfce appearance. The Applications menu now reads Xfce Menu, all my launcher buttons are blank and unconfigured, and the clock settings are gone.

How do I fix this to get it back to the way it was before?

Thanks for the help.