I doubt this is a Permissions issue -- running Permissions repair is harmless, but probably not needed -- but do not run Repair Permissions booted from the Snow DVD. This will almost inevitably introduce Permissions errors where there were none. You should repair Permissions booted normally. This is what Apple recommends. For a full explanation, see my post here
https://discussions.apple.com/thread/3124635?start=0&tstart=0
Sometimes, preference settings may come unglued due to low free drive space. Select the HD icon and do a GetInfo.
If this continues, you could try moving this file found in your user Library/Preferences to the Trash (don't empty yet.) Re-open Sys Prefs; a new preference file will be created automatically.
/Users/yourusername/Library/Preferences/com.apple.systempreferences.plist