voip and firewall

[Erez D]

hi

my company just installed a new firewall.
i had an ATA (grandstream handytone) that was connected via the internet to asterisk at my home

this ATA does not work anymore ( i can dial, but have no incoming audio, people can dial to me but it disconnects when i answer)
this is due to the new firewall.

however, i have a voip software (x-lite) that works very well, even with the new firewall.

can anyone tell me what is the difference (and how can i make my ATA work again)

thanks,
erez.

btw. please no tunneling solutions etc ...