I can not craft. the game will not allow me to pick up the items in my inventory... help...

I have been playing minecraft for a while, and I have NEVER had this problem before. Every time I get into my inventory, I can not pick up any of the items. my buttons haven't changed, I have not done anything to my minecraft except update it, and, yet, I can't move a THING in my inventory. I have been trying to pick things up in my inventory by using the left mouse button, but it won't even allow me to pick it up. I try using the numbers, but I can't craft anything... What am I suppost to do about it? Please help me out if it's just a glitch in my game... it's annoying me more than you think.