iTunes can't connect to iPhone

I'm using the latest iTunes and iPhone 3GS, 32gb, and mostly it works fine.

But if I login to xp and the domain is not available (at home), iTunes says "unknown error" when connecting to my iPhone?

I have been able to connect to the iPhone without the domain available, but then the connection is very slow usually hangs after a while.

But iTunes shouldn't be affected by the domain, or DNS-settings, should it?