Issues with airport and my netgear router and Entourage

I have an iMac running OSX 10.5.6 which is hooked up wirelessly to a Netgear DG834N router. I also have an HP Windows Laptop and a Logitech Squeezebox which are also hooked up to the router.

Earlier today (and not for the first time) I got a pop up message that said (***imac.local-2 is already in use and has been changed to ***imac.local-3), so I went and changed this back to ***imac.local. My airport then dropped its connection with the router and wouldn't come back on.
I could get my laptop to connect, but only at 1.0 mbps. I changed the channel on the router to channel 1 and things got a bit better, but it was only when I changed to channel to 7 that I could get the airport to connect again.

Now my Entourage won't work and won't send or receive any email. I get error 17900 and I get this error:



I have checked my account settings in Entourage and can't see anything wrong with them. The password and username are definitely correct. I use gmail, which I know is prone to the occasional problem, but gmail webmail seems to be functioning fine.

Any thoughts?

my path in troubleshooting would involve disconnecting everything and starting back with powering up router and then turning on iMac and connecting wirelessly. At that point take stock with Entourage and see if it plays nicely. Make any needed changes to network at this point. Once past that phase then add back other bits one at a time making sure that Entourage is still happy. If that is not a go, then do it all again using ethernet to eliminate a wireless setting issue. Somewhere in that process you should get a indication of where to look for your conflict.