You'll have to see how you feel. I would say you probably won't be able to for a day or two. But that's just how I used to feel (I can't give blood anymore because I lived in England--mad cow disease & all).
Deborah- I'm another one who's ineligible (grew up in Europe). I think there are more of us than they think they are.
When I was allowed to give blood, it usually took two full days before I could work out again and three before I could work out at full steam. But that might just be me.
I am usually ok the next day. Drink lots of water and eat well to restore fluid and nutrient levels and listen to your body. You may want to modify your intensity a little. It's certainly worth trying as long as you err on the side of caution.
Chicks's Rule! http://www.handykult.de/plaudersmilies.de/chicken.gif Bobbi