Asterisk and Nokia E71 thru NAT

Hey all,

this is my first post so i hope its in the right place.
We have asterisk at my work place and are starting to role out the Nokia E71. I have got this working thru the NAT etc. If i call the E71 ext it goes straight thru. But if i call an extension or other number it can take between 1 min to 2 mins.

This is all external to the internal network(which works straight awa)

i am testing from an ADSL2+ connection with 700k/b sec d/l speed so this shouldnt be the problem. Just wondering if there is anything i can check to see what the problem is?

any help would be great

thanks ,