Can't change dock size...

For some reason I'm not able to slide the slider on "Dock Size" in system prefs. It's all greyed out. Also, I can't get the double arrow to do it from the dock. Anyone know why?

I dont usually bump my stories but this is really annoying and I can' find anything on the internet about the problem. Sorry.

I would give OnyX a try. Repair permissions, run the maintenance scripts, clear caches, check for corrupt preference files, etc... The only time I've seen it grayed out, is when someone didn't have administrator privileges, or was set not to have access, due to parental controls.

Delete com.apple.dock.plist from your home > library > preferences folder.