Screen Share Issue

Hi Guys,

I did a search on this but could not find my exact problem, so here goes.

I have a macbook pro, macbook and an Ibook, now i can do file share with all of these machines on my network, but i can't seem to do screen share with any of them, it just won't connect and says i may have a network error. (but i can file share between all 3!)

They all have thier "back to my mac set up", the router has UPnp set up and i tried to setup up port triggering on port 5900 which apple uses for vcn connections, but it won't let me set it up as the port is being used. (i am guessing that is because i use the file share)

So now i'm at a loss how to get this to work.

Can anyone point me in the right direction as this is giving me a headache, and i have alot of patience, i don't feel i'm an idiot with macs, but this sure is annoying.

Regards

Dmac