Skype randomly chooses ports upon install for each device. That way there is a very small chance that one of your other computers with Skype might conflict with another device on your network. Of course, this randomization isn't perfect. You should drill into your N800's Skype settings as follows:

launch Skype
(top left corner) pull down menu
then tools
then settings
then connections (tab)
look at the port Skype chose, it should be a fairly high number

You can change that port to something else but you do not want a port which might conflict with another application to another computer in your LAN. Keep your choice high but below 65000. You don't want any other Skype software on your LAN using the same port as another Skype device on your LAN.

Get a computer and run NetStumbler, (or use ministumbler on your Pocket PC) and verify that your router is on a unique channel and that no other wireless networks conflict or overlap with yours. (If you have a neighbor with a WLAN his wireless could effect yours. Your N800 could be connecting to a AP that is next door instead of yours. Check that out. Try turning off encryption while you are testing too, you can turn it on again later (don't forget).

Check the box in Skype connection settings that says, "Use port 80 and 443 as alternate incoming connections." If that doesn't help, uncheck it.

Search a post here on this site that talks about N800 powersave WLAN timeouts. Read about what that is, and change your timeout to 1000 by following those instructions. I'd give you a link but I cannot remember the thread. Search it.

Remember the port setting for Skype? It is a high numbered port. Drill into your router and open that port to the Internet (port forwarding). That will help Skype in the event you have NAT transversal problems causing your audio symptoms.

Good luck

M5

EDIT : You will need to know what IP address was assigned to your N800 on your LAN for the purpose of port forwarding. DHCP will cause your computers to come up different with each boot. So will your N800. It won't do any good to port forward the wrong IP, you need to use the IP address of your N800 during these tests. Tools<connection manager(top left corner pull down)<Internet connection<IP address gives you your N800 IP for that session.