1) Used to describe the situation in which your laptop shuts down while you're doing something important, such as cyberflirtimh with that cute redhead girl that just moved in down the block, or typing an essay for english class.
Derived from a rarely used slang term, when something "craps on you", meaning that it gives out on you, or embarrasses/makes things worse for you.
"And that concludes the memoirs of my life. At my old age, I simply cannot type any more. So, good night ever-
*FATAL SYSTEM ERROR COMPUTER MUST RESTART*"
"Dang. Lappy Crappy."