There can be lots of reasons for this - I have experienced it when my preferences became corrupt.
There are various ways to reset your preferences in indesign but please note that replacing your preference usually means you will need to set them all again.
Not sure what version or OS you are on but you can do a quick preference reset when you launch ID by pressing the following keyboard short-cut.When launching ID IMMEDIATELY hold down Ctrl + Alt + Shift (Windows) or Cmd + Ctrl + Opt + Shift (Mac). You will get a confirmation window asking if you are sure - if you don't get that then you were too slow.
The other way is to do it manually - this way you can back up your preferences before resetting them just in case it isn't a preference issue - then you can put them all back! More details here...http://indesignsecrets.com/rebuilding-indesign-preferences.php
Please go to the link below and follow the mentioned steps.
Steps are easy to follow and should help you resolve the problem.
Let me know if it works for you..
Some problems are platform or version specific. Exactly what version of InDesign and computer platform?