Why can't I craft anything with items from cheats?
The command you have used is incorrect, the format for giving items is:
/give <player> <id> [amount] [data]
So as you can see, you've actually given yourself a stack of 64 diamonds with a data value of 264. The kind of diamonds needed to craft armour with has a value of 0, and so the recipe doesn't work.
The amount and data values are both optional (hence the square brackets), with the amount defaulting to 1 and the data defaulting to 0.