Whenever I craft a computer in Tekkit the game won't give me the item?

I'm just starting off about ten minecraft days in and I have enough resources to make a turtle, but whenever I try to craft a computer, I'll take the computer and try to put it in my inventory but it pops right back. If anyone can help me fix this problem, it would be much appreciated.

That usually means the item is only craft-able in peaceful or creative mode, I had the same problem trying to craft a watering can in FTB, turns out that recipe was a peaceful recipe only. Check to see if there's another crafting recipe for that item, most of the time it's only 1 extra item to craft it.