Good to know Chris. If the problem is persisting in your own account you can try this:
Locate:
"com.apple.finder.plist"
and change it to:
"com.apple.blinder.plist" or something else that's not already there.
Also locate:
"com.apple.sidebar.plist"
and rename that suitably, eg:
"com.apple.sidepar.plist".
Log out, then in again.
Relaunch the Finder by choosing Force Quit from the Apple menu, selecting Finder, then clicking the Relaunch button.
Empty the Trash.
Check to see if things are alright. If they are you can trash:
"com.apple.blinder.plist" and "com.apple.slidebar.plist" ...
if not, then trash the new
"com.apple.finder.plist" and "com.apple.sidebar.plist"
Then change back:
"com.apple.blinder.plist" to "com.apple.finder.plist"
and:
"com.apple.slidebar.plist" to "com.apple.sidebar.plist".
The problem is elsewhere.