I cant freeze anything on my physics gun!

When i pick up a prop with my physgun, and i right click,the prop just falls and it does not freeze. I cant get it to freeze!

Please Help!

Stupid question, but are you making sure you do the transition between holding the prop with left click to freezing the prop with right click? Also, are you making sure that when you do freeze the prop, you do not accidentally click it again?