First thing I would look for is: Is there a preset that is being applied in the Develop Module? To test this click on <Reset> at the bottom right, just above the film strip.
If <Reset> doesn' help, I would think of a "corrupt" Preference File:
This file can go "funny" and is then responsible for all kinds of strange behavior of Lr. The remedy is replacing the Preference File.
BTW: Re-installing Lr does not replace the Pref. File since it is designed to "survive" upgrades.
See here for where to find the Preference file for your OS: http://helpx.adobe.com/lightroom/kb/preference-file-locations-lightroo m-4.html
See here for how to go about Replacing the Preference File: http://lightroomers.com/replacing-the-lightroom-preference-file/745/