I was a Information Technology supervisor for several years....from my own experience, I only had one guy who was the employee from hell.
At first, I tried everything with him. Praised him,, gave him additional projects (so that he would be recognized along with the rest of my group). Tried the friendly appoach. Showed him special treatment. Gave him a good review for a pay raise. Nothing worked! He continued to torment me, in ways that you had described and more. (always late for work, long lunches, went through my desk, leave early, sending IM messages all day long, work not being completed. etc...)
After months of this, I finally found him gambling on-line at work and turned him into HR. I thought that he would be terminated, but they gave him a verbal and written warning. Two days later, my car was keyed and scrached on both sides (from front to bumper)!
Since I didn't have any prove that he had done this to my brand new Acura, I did the next best thing. I went to upper management and had him moved to another department.
Believe me....get rid of the headache!
Dee