Strange Windows XP Network Problem

Hiya,

I have the following setup
Windows XP tower with nvidia chipset and LAN controller connected to a Comtrend CT-5361 router via ethernet cable. All was fine until a few months after I had added an TP Link TL-WR740N access point to extend the range outside, connected into the router via ethernet.
Now if the access point is connected to the router the PC says network cable not connected.
If i connect my laptop into the router via ethernet that works fine
There is no IP conflict - router 192.168.1.1 AP 192.168.1.2
Ive tried the PC as manual 192.168.1.30 and via DHCP but no luck
I can connect to the AP via wireless Ok as well

This problem didnt happen immediately after adding the AP so I think it may be related to when I cleaned up some malware from the PC using Malware bytes and combofix

Any ideas?
TIA

It's a tricky one. I too had a similar problem, but with home plugs that would just die when the AP was connected to the network.

One suggestion I received was to change the MTU, but the AP in question could not do this. Perhaps yours can - best bet it to make sure all units on the network have the same value, especially the router and the AP.

In reply to a post by slippyjim:

the access point is connected to the router

Which port on the access point is connected to the router? LAN or WAN?

use device manager and remove the ethernet device, then let XP auto install ethernet again

its connected to the LAN port

I've tried this several times witho no joy

I'll have a look, but it was a cheapish AP so I don't expect too much

you could get this sort of problem if the access point has cloned the mac address of the computer

How can I stop this happening?

ok, I had the same when I removed one of the anti virus engines. It did not remove itself correctly and left the network in a bad state. It was part of the LAN registry settings that were corrupt. I had the ability to do a restore to before then problem and then did the uninstall again. That fixed it. I suspect your reg settings are broken some where and hence you have a problem. Not sure what tools you can now use to fix it.