I have one that's doing that now. I had another die (while my covey was being cared for while on vacation) that may have had a similar condition. Lethargic, can't walk, falls over face first. Doesn't want to eat or drink. He seems strong enough to walk when I handle him, but it's like he has no balance/coordination. I have him in quarantine for 3 days now. He's at least standing and I find him in different areas of the cage. Won't eat sliced grapes, meal worms or food. It's like he's too confused and freaked out.
I've read about possible Mereks disease (look for watery diarhea) or even H1N1. All other birds in his large cage (20) are fine, as well as the two other tiers. Cage was cleaned from last birds with clorox water a month before. Feet look fine. Wish their was a bird Dr around. Dr Pol?