Are you getting events in the event viewer every few seconds? Event IDs 50034 and 50068? The text of event 50034 is “An error has occurred in initializing the adapter 15. Error Code is 0x1392″ (perhaps a different adapter number), and event 50068 is “Address 192.168.1.100 being plumbed for adapter 15 already exists” (with a different address and/or adapter number). Here’s the solution:
First check if one of your adapters has a static IP address that you assigned it.
If not, then just disable one of the adapters. Suddenly the other one will be connected no problem. The reason is simply that one of the adapters was previously assigned address 192.168.1.100 (or whatever your error is saying), and even though that adapter is disconnected, it is still conflicting with your new adapter trying to become 192.168.1.100. The DHCP-client service won’t assign two adapters the same address, so it keeps renewing attempting to get a new IP, but the DHCP server (your router) keeps assigning it the same conflicting address.
It’s safe to leave the adapter disabled, but if you don’t like the idea of having one of your adapters disabled even when it’s unplugged, then re-enable it and plug it in to something which assigns the adapter (via DHCP) a new address. Then Windows will allow your other adapter to take the address it has been trying to get all along.
I saw this in my own laptop. It has an ethernet adapter (Local Area Connection) and wireless adapter. The ethernet was unplugged and I was trying to connect to my wireless network, but the wireless network kept connecting and disconnecting repeatedly. The solution was to disable my local area connection adapter. Then suddenly the wireless one was connected! The underlying problem was some static DHCP settings I had set in the past.
Also, if you’re reading this and it fixed your problem, you probably also enabled static DHCP like I did. If so, make sure to assign a different IP to each of your adapters even to the same computer; i.e. assign 192.168.1.100 to the ethernet adapter and 192.168.1.101 to the wireless adapter. Even if they will never both be connected at the same time, this and other problems can arise by them being set to the same DHCP address.
Hope this helped you. Feel free to add any other information in the comments below.