Now that I am here, I am sure the flaming will stop and we will get back to the thread. Right?
First, you may have a slight concussion. That is quiet possible. Look at the timeline of how you were feeling and see if it adds up.
Now, ruling that accident out - the thread still has merit because quite a few people hit that "slump" midway or towards the end of their cycle. There are quite a few reasons for this.
When you are on cycle, you are training much harder than usual (or you should be). This is a dramatic increase to the usual stress the CNS has had to cope with. Most people think recovery is just about whether the muscle has recovered from the last workout and can be worked again. But it also applies to the CNS system as well. Heavy training definately affects it. You will eventually burn out if you don't take precautions.
Take a week or so off and recharge the old mental batteries. Do things away from the gym. Have fun.
If you come back and still notice a slump, then consider using something like PPs products. The Dermacrine definately perked me up in the gym. The mental focus was extremely heightened. Also consider a mild stimulant like Provigil (sp?) It is a clean stim, no jitters, no crashing, just clean energy.