I've been running for about a year now. Every race that I do, or every longer run (greater than 5 miles), I feel sick afterwards. It starts about 30 minutes to 1 hour after I'm done running, the stomach cramps hit, diarrehia (sp?), chills (like I have a fever), and overall lethargy. This will last from anywhere from 2 hours to 12 hours.

Is this normal, what is happening? any suggestions or experience with this?

It could be that you have blood sugar problems. when I work out, mine shoots real low, and i feel so bad. try eating a good meal (not too heavy) and possibly a glass of sugar water to get your body going before you run!