Dworgi same problem I have too, Greaper is also having this problem and maybe more people
We have Speedtouch 585 v6/v7 routers, its something todo with the router not supporting full cone NAT.
I dont know what this does exactly but it does fix the problem - but you lose it when router reboots.
See -
http://forums.multiplay.co.uk/showthread.php?t=51306In Windows
Go to Start, Run and type cmd
Then type telnet 192.168.1.254 and press Enter
Enter your username and password (by default username = Administrator with a capital A and password is blank)
Then type the following exactly as shown below and press Enter after typing the 0
:connection bind application=CONE(UDP) port=0
Then type
:saveall to save the config changes
Type exit to quit
Go to the modem web interface (internet explorer to http://192.168.1.254) and restart the router
Again when you have telnetted to the router (see above), type the following
:ids config state disabled -> Press Enter
:connection appconfig application=CONE(UDP) timeout=0 -> Press Enter
:saveall -> Press Enter
Go to the modem web interface and restart the router