I too am having problems with this.
I used to stream video frequently, once for over 8 hours straight with no significant problems. I thought I was done streaming so I uninstalled the program. Now I find a reason to start up again and have downloaded the most recent version only to find that after about 20 minutes it starts to act up and the CPU usage spikes to 100%. Closing the procaster produces a significant drop and the video runs fine. However upon reopening procaster I am immediately hit with 100% CPU usage. Even if I have all other programs and non-essential operations closed including the video. The only thing I can figure is that the problem is somehow caused by procaster itself. The only way to prevent procaster from utilizing all my CPU is to completely restart, and again things run for about 20 minutes before it hits a complete breakdown. Testing this I have found that simply running procaster and streaming simply my blank desktop causes my CPU to spike after roughly the same amount of time.
My computer meets or exceeds all specifications stated under the 'Recommended System Specifications for Broadcasting' section here: