Sometimes, InDesign just goes crazy. If it does, save what you're working on and do the following:
- (Windows) Start InDesign, and then press Shift+Ctrl+Alt. Click Yes when asked if you want to delete preference files.
- (Mac OS) While pressing Shift+Option+Command+Control, start InDesign. You might see a popup menu, in which case hold the keys and choose Open. Click Yes when asked if you want to delete preference files.