Fantastic-Pet-Rats

Hi, I'm hoping someone might be able to offer me some advice for one of my young rats.
He is only a couple months old, and I am told he was socialized by the breeder he came from. I bought him from a very good, pet-only pet shop, and he has been checked out as physically healthy by my vet, who is a pocket-pet specialist.
While his brother has bonded with me, will take treats from my hand, run around with me and ride on my shoulder like he's been doing it for years, this little boy, named Silvua, is still extremely nervous and shy.
For a short while, I felt I was making some progress with him. He would come to me from their cage and climb up my arm to perch on my shoulder, he would even try to 'play dentist' if he was sitting on my shoulder while I was talking. He enjoyed sitting in my shirt while I was on the computer, and would brux if I pet him in the right spots. This lasted for almost a week.
Then, suddenly, he reverted back to his earlier nervous behavior. He often jumps at the sound of his name, squeaks at me when I try to pick him up, will make a mad dash for any sort of cover when he's out of the cage. He'll watch me and act like he wants to come out and play, but when I get up to talk to him he runs away and hides in their igloo.
This has been going on now for two days, and I'm beginning to worry that there is something mentally amiss with him. Does anyone have any suggestions on things I could try to calm him down and help him learn to trust me?

I wanted to share this for all people who think breeding is fun. 
A new simulation game has just been made, that simulates Australian rat breeding (so you won't get dumbos unfortunately). It's really fun and we're looking for more people 

www.virturatz.com/

Give it a try! you won't be disappointed

I forgot to give my thanks for accepting my request to become a member of this group! Thanks a bunch!

did you even bother to check what you have accepted to your group.. the picture here [link] is of a dead rat the poster admits in his comments was killed by him... sick

you should not be accpeting horrible images like this.. its sick as hell.

thanks for my rafael and laureus pictures

i was wounding if any one know any good names for 2 girls rat ?