virgin 100 meg hub

hi got my 100 meg fitted today with a virgin super hub but when it comes to port fowarding it just wont open the ports for my servers ? so when i use it ass modem only with my old router everthing works fine but i only get 20 meg ???? hope someone can help me its doing my nut in lol

the only work round i have found is turn the super hub into a modem only in the settings menu then use your own router to to the port forwarding and dyndns updater ? everything works ok then