i have noticed that the REASON WHY some members cant access other memberz hosts is because you have set 'YOUR NAT TYPE:STRICT'. The NAT TYPE message is on the menu where you 'create a class' etc.
In-order to connect to each other smoothly, you need to have 'your NAT type:OPEN'.
Because everyone has different 'brands/company name' routers, the method of changing it from STRICT to OPEN would be diffrent for all. Therfor could you provid me the 'brand names' of your routers, so that i can find out how to sort this out for you.
P.s when your NAT Type is STRICT it will prevent your computer to be accessd by someone else when they try to connect to your host. They get blockd out.