This may or may not apply to Debian or to your problem, but hopefully this will be of help to you. When installing SuSE 9.2 on my brother's notebook, the wireless card was recognized and configured, but internet only worked through ethernet. There were two things wrong, which we fixed, and now it works just fine.
1) He didn't have his password/authentication mode properly setup (I'd check that first).
2) There was an option set on install that always deferred internet to the ethernet card, regardless of whether or not it was connected to the network. The fix is decribed here:
http://portal.suse.com/sdb/en/2002/1...cp_client.html
Be sure to apply the instructions for both wireless and wired connections, then restart the network or restart the computer. I hope this is what you are looking for. Can't hurt, in any case.