I don't think that's too much sodium at all. Especially this early in the season when you're not acclimated to the heat. It might not be enough. A pharmacologist is not an exercise physiologist ...
http://www.ncbi.nlm.nih.gov/pubmed/18226265 - (550-750 mg/hour sodium lost in sweat)
http://www.training-conditioning.com...eir_sweat.html (layperson's summary that I didn't chase the references, but claiming 1-2 g/hour sodium lost in sweat in a study of football players)
Personally, I'm so prone to a mild hyponatremia that it's (finally) the first thing I suspect any time I'm nauseous. I'm not even a particularly salty sweater when I'm acclimated to the heat, but I do sweat profusely, I eat mostly real food, and I have to be very liberal with the salt shaker and the Zenergize (500+ mg sodium per tablet) to avoid problems whenever I'm doing much of anything outside.