802.1x Authentication has failed. Error: 1 on port en1

I have gone over and over many other posts on this today all to no avail as most discussions are specific to particular networks. Usually US universities.

Anyway..

I have multiple MacBook Pro's on site and have been using RADIUS authentication for some time by manually installing a certificate in the system root for the local DC, and then creating an 802.1x login window profile. Recently however a couple have stopped working.

I have 2x MacBook Pros. 1 a 15" on 10.5, another a 13" on 10.6. Both have BCM43xx AirPort cards. They were originally OK until after a Mac Update, which made us believe it was the firmware version of the airport which had caused the fault.

I have however rebuilt the 10.6 client to 10.6.0 and upgraded 1 patch at a time to 10.6.4 until it reached the identical airport utility and bcm43xx firmware version as the working clients, however still to no avail. When trying to connect to teh Wireless network, i am prompted for credentials which i enter (work on another client) and it instantly rejects them, without even thinking about it. VERY LITTLE is shown in the system.log, other than the en1 starting, then stopping within a second.

I've wasted 2x days on this now and would really appreciate some assistance if anyone has any ideas. Otherwise it looks like I may be having to create a whole new SSID with WPA2 keys, rather than RADIUS and I would prefer not to do that.

Thanks in advance,