Very Strange Connectivity Issue.

We have Sprint DSL (Embarq 660 modem) with a Linksys wireless router, BEFW11S4 with the following systems:
1. Desktop, XPHome Sp2, directly wired through the router.
2. Laptop 1 - wireless. XPPro Sp2.
3. Laptop 2 - wireless. XPPro Sp2.

Yesterday, laptop 1 started giving the "Limited or No Connectivity" message. It has been working well for 5 weeks. I have WEP enabled.

Today the desktop started to give the same message - this has been working well for the whole year.

Laptop 2 still connects - I'm using it to post this.

I've power cycled both modem and router more than once.
On laptop 1 I've re-input the WEP key more than once. I've tried two other wireless adapters without success - same error message. I've tried a different hard drive which also used to connect.

On the desktop I've used another hard drive which connected as recently as yesterday, as did the original hard drive, - no joy.

I'm really puzzled as to how this laptop 2 still connects but neither laptop 1 nor the desktop will not connect to the Internet. Any suggestions?

 

Update: I took the Linksys out of the loop and connected the desktop directly to the DSL modem and now the desktop connects. I am going to try re-doing all the settings on the Linksys and see if the desktop will still work.