I use Win2k Prof
I created my profile while attached to the domain.
When I go home I have a wireless connection to the broadband.
When I log in from home, I login to a cached account as stated above.
I have the same profile on and off the domain

My profile name is just my username.
I think it would only create name.domainname if you create the profile at home, and then attach to the domain with a domain account. So essentially having two different users with the same username as far as the laptop is concerned.
bottomline...
Create the profile while attached to the domain, then you should be able to logon from home as needed on a cached account
SRJ, if you're on DHCP thats not really an issue. If you're on different Network adapters entirely (much like I am) is the best solution.