Very nice piece of flash!
Firstly id like too say that i personally have had experience with somebody with this disorder and the way you have depicted it worked very well.
Bipolar causes a persons state of mind to completely disintegrate into a state of mania and complete and utter depression and with this flash you have really captured this. The smashing on the head with the metal pipe certainly portrayed this.
I really liked the way you created the voices that were trapped inside the boxmans head. This made the viewer of the flash understand what was going on a whole lto better.
I also liked how the desk moved farther away and the significance of it only being that one person in a room gave off the feeling of unhappiness and loneliness, well done.
There are no major issues with this piece of flash at all. It was a well drawn out, short animation. The only advice i would give too you is that in parts the animation didnt flow aswell. By this i mean that in one scene the man had blood pouring out of his face and in the next scene he wasn't. I'm sorry to pay attention to detail but little things can make a difference in flash movies.
Overall, i wasnt dissapointed, this was a good piece of flash and i enjoyed watching it. =]