I can't remember what the exact dose was, but I took it in powder form - it is actually called "Natural Calm" so you can imagine my surprise when I was an anxious wreck 15-20 minutes after drinking the stuff. I have also heard of people becoming anxious on a high dose of b vitamins.
Where are you getting your supplements? If you're paying for top of the line stuff, it can DEFINITELY have a different effect than typical drug and grocery store brands. The more expensive stuff is usually more potent.
This could be your answer, but antibiotics can certainly cause this as well. A herx can take shape as anxiety too. There are a lot of factors here.
Current treatment (began June 10th 2009):
Biaxin 1000mg/day, Pulsing Flagyl 500mg/day 1 Week Every Month