Cannot re-join wireless network with MacbookPro

I cannot get my MbPro to rejoin my wireless network. It tells me that I either have an incorrect password or chosen the wrong type of security etc, none of which is the casel

The problem arose after I wanted to transfer some large Aperture libraries from my MacBook to my Macpro. I used an Ethernet connection straight from the laptop to the MP rather than the wireless for a faster transfer. So disabled the wifi, did the transfer but know cannot connect to the network. I've done this many times before and never had a problem. I am surprised that the laptop just didn't remember my password from my keychain anyhow.

Any suggestions please.

By the way I am not using my Airoprt base station due the ISP providing the hardware. Tried to use the Abs to extend the network but although it shows up as working it seems to block connection so stopped using it.