Protein powders give me insomnia too. It's strange because I eat meat all the time and never get insomnia. I have found that if I start off with a 1/8th scoop and increase over a period of a week or two till I get to a whole scoop, then take regularly at the same time each day, I don't get insomnia.
But, I've been doing some research and I've read that protein blocks the production of serotonin.
Also, I've read that tryptophan (found in high concentrations in some meats) can help increase Serotonin and make you sleepy. But, tryptophan may not cause you to be sleepy as much when eaten with meat because it has to compete with other amino acids.
Also, when I read my protein powder jar, it says "contains no added L-tryptophan"
So, as a guess, I'm thinking if that these amino acids are not in balance, you will either have insomnia or become too sleepy.
I'm going to try taking L-tryptophan as a supplement with my protein powder and see if it makes my insomnia go away. I will post my results here. If any one else tries it or has tried it, please let me know if it works.