W2K Server, DHCP and Superscopes

I have a DHCP server running W2K with a superscope and 5 scopes underneath. The problem is that one scope is down to 3 IP addresses but out of the total 5 scopes, I have a total of 189 IPs available. I can disable the one scope that’s down to 3 IP addresses and then DHCP starts handing out from a 2nd scope. Why doesn’t DHCP hand out IP addresses evenly across all scopes? I’ve run into trouble where the one runs out all together and DHCP stops handing out IP addresses. Any thoughts would be appreciated… If you need more information or a clearer explaination, please let me know.

Thanks,
Laura