I am making a model and in object mode, you can't rotate, scale, mirror, etc a mesh. The only way to do it is to got to edit mode, select and then rotate. That worked for me until I made a armature and you can't rotate it in pose mode!
It sounds like you have Manipulate origins (⎇ Alt,) enabled in 3D view > Header:
This setting makes it so transforms will only affect the origins of objects, rather than the objects themselves. This is only really very useful when you have multiple objects/bones selected.