AFP 10 user limit

Hi There,

Our server (10.7.5) has recently started to limit the number of AFP connections to 10; perviously it's allowed ~15 connections, but now the 11th person trying to connect gets;

"This file server will not allow any additional users to log on. Please try to connect again later"

I understood there was no limit to the number of AFP connections. Any ideas as to how we might configure it to allow for 10+ connections.

Thanks

Ben