When asking for technical help here, there are several things you should consider sharing based on your type of situation. This info can always be asked of you, but you may speed up the flow of ideas.
What's your operating system, Windows or Mac?
Are you using Mods or CC? (without getting too specific)
What Expansion and Stuff packs do you have?
When did you last uninstall/reinstall the game?
What were you doing at the time of the issue?
Is your game up to date? What is your current version?
