I had my 770 for about a week, and so far ran into only one persistent problem with WIFI: when I try to connect to my office network, I get the right IP address, the mask, and the DNS, but the Default Router field remains blank (none). As a result none of the internet apps work.
When I connect at home, everything is working fine and every field including Default Router are assigned. I couldn't find a way to set Default Router permanently on my office connection.
Any help with resolving this issue is much appreciated.

TIA

im not sure on the 770 but on the 800 you go under conectivity in the control panel edit the connection and go through the wizard till you see a button labeled advanced. theres a tab for ip addresses. you can set the ips here.

it sounds like your work dhcp server isnt sending the gateway for some reason.
you should be
able to set the gateway with. of course you will need a xterm and gainroot for this method.
you could probably get this ip
off a work computer on the same subnet as your wireless ap.

The problem with static IP is that the DHCP leases are very short and I cannot pick an IP address that will be mine for any length of time. In fact, every time I connect, I get a different IP. Also, my laptop wireless connection is fine and I always get the correct default router.
I tried the route command you suggested, but I got 'Network is unreachable' error....

Sorry i couldn't help Things like these take lots of trouble shooting.
heres some more commands that you can use to find info for trouble shooting
will give you some routing info
will show you name servers.
will give you your network settings.