I can't transform into a werewolf anymore after installing Dawnguard. When completing the companions questline, when Farkas and I are ambushed by the Silverhand (and I just have to watch through that gate), instead of Farkas transforming, I just watch him beat up the silverhand bare-handed... For some reason, when they turn me into a werewolf, I turn into one for the very first transformation (immediately after the blood ritual) but after that I can't transform. I use the power and nothing happens except I can no longer access my inventory. Has anyone else experienced this bug? It's maddening.

I have a simular issue... I completed the companions, became a werewolf and while I still have all the powers of a werewolf, the option under POWER to select/use to turn myself into one is gone.

I still have restless sleep, disease immunity and what not and I know I didn't cure myself.

Guess I could always try and cure myself and have Aela turn me again and see what happens.

I had a similar problem with inability to transform correctly. I found out this was caused by incorrectly installed mods though.