This is a problem when you update from 0.91 to 0.92... :/
If you don't care too much about your preferences, I remember that the easiest way to fix it would be to just rename the preferences file that you have, and see if that solves the problem.
Find the location of the file via Edit > Preferences > System : User preferences.
You need to close all Inkscape windows, then rename the file, then restart Inkscape for this to take effect.