Wireless Networks not found with WNDA4100

Hi

i have a pretty weird error i cant find a resolution for:

I have a pretty complex Wireless Setup in my house starting off a R6250 Router and four workstations.

Two run an older N300 adapter, and i wanted to upgrade my main core PC to use a better broadband connection.

I previously had used the WNDA4100 on this one and used the 5Ghz 801.1n standard on my main machine, all fine i get about 85Mbit rate over two floors, thats fine.

I wanted to upgrade my other machine as well, moved the WNDA4100 to that (also Windows 8.1) and installed a new fresh AC1200 on my main machine with 801.1ac on the 5Ghz channel. Fine i get 120 MBit rate on my main machine. That so far works great.

My older machines on the 2.4Ghz channel still work.

Now i wanted to install the WNDA4100 on my second machine, installed the drivers etc, but that now doesnt pick up MY wireless networks anymore. It finds all networks in my neighbourhoud but not mine. Not even the older 2.4 GHZ networks, just nothing. I tried removing the drivers, reinstalling, no joy. I though it might be down to the signal, moved the PC right to the router, still the same. All neighbourhoud netwroks, not mine. I plugged in the N300 adapter. fine, works, get my networks (just not the 5Ghz ones, that is understood).

Plugged the WNDA4100 to my main PC, works fine.

Just on that second machine it doesnt find my networks, but others.

I tried deleting the Wireless profiles, no joy.

Even looked up the registry, no joy.

Any ideas are welcome.

thanks