XP Home/Pro networking problem

[P2Mc28]

I've got a strange problem. I've been bringing my computer over to my friend's house and LANing for over a year, no problems. We both ran Win XP Home, and everything was fine and dandy. However, I rescently upgraded my computer and installed XP Pro instead. Now when we try to LAN, we can both connect to the router just fine, access each others files and whatnot, but neither of us could go online! We found that telling the router to disconnect/reconnect gave us both access to the Internet for about 10 seconds, then it stopped. Also, if my computer is idle, his computer can access the Internet just fine, and vice versa. I have more or less narrowed the problem to XP Pro by formatting and installing each OS again. After putting Home back on, we could both go online and everything was fine. I re-upgraded to Pro and the problem came back.

Help?

 

[P2Mc28]

Well, if no one knows anything, any helpful information would be helpful. I've been doing google searches and looking thru Microsoft.com, but due to the nature of the problem all I'm getting are people with problems about Pro or Home, not people trying to network Pro and Home.

 

[MichaelD]

It sounds like his ISP is using MAC tables to authenticate access.

I.E. it's looking for the MAC addy of HIS nic and it's seeing yours/both addys, so it's not permitting access.

OR

Is his router running as a DHCP server? Are both of your PCs set up to get an IP and a DNS server automatically?

 

[P2Mc28]

Well, I don't think his router is looking for MAC addresses because A) I don't think it's a default setting, B) I set the router up myself and didn't fiddle with MAC authentications, and C) it works fine on XP Home, and doesn't on XP Pro, and MAC addys are hardware indepentent, not software, right?

Secondly, yes the router is running as a DHCP server and both PCs were configured to use it.

(NOTE: I'm at home now, and my PC seems to interact with my network here fine, although the other computers, which all run XP Home, are probably not on right now and I don't have time to test it. I'll post some more info when I get home from school)