Co-worker impossible to work with

I work about 40 hours per week from home. I feel very good that I am able to stay at home, while earning much needed money for my family.

My job is a bit technical and I have had to basically train myself. Each month I must file a report, which a number of people's salaries is dependant upon. There is a ton of pressure, but it is rewarding.

I have one person who I work with who is extremely difficult. (Yes, I have spoken to the boss, who has spoken to him, but it hasn't gotten much better!) He does not hand his work in on time, causing me major delays. When it is handed in, it tends to be incomplete or wrong. I have asked him on numerous occasions to please be more careful with things, yet he continues to make stupid errors because of his carelessness. When confronted he comes up with stupid excuses, which I see right through as being false.

I needed to train him for something a few weeks back. He insisted rather than doing this technical training in person, that he only had time over the phone. He reassured me that he understood everything completely. When it came time for him to do the work, he told the boss he didn't know how!

I had a major report due a week or so ago. Due to a number of major extenuating circumstances, I was very behind schedule. I asked the boss if this guy should help me in meeting the deadline. The boss said considering everything, yes he should help. I sent him e-mails which he ignored, tried to call him, etc. In the end the boss got through. He said he'd do it for sure. In the end, he did not do an ounce of the work!

I am so frustrated with him! Any advice on what to do?