Ethernet LAN and WIFI / WLAN not working simultaneously

My laptop used to be connected

1. wirelessly to a wireless router and
2. physically to a switch via ethernet cable to access other PCs on site

For years, I was able to

1. enjoy wireless internet access and
2. transfer big files to my other PCs via ethernet, having prioritised the LAN connection

All was well. After two months absence from work, I found the wireless router was broken, so I bought two new ones, same model as before, just in case. Windows 7 Enterprise also updated in the meantime.

Now, when the ethernet cable is plugged in, I have no wireless internet access ("Attempting to Authenticate... forever); when the ethernet cable is not plugged in, I have instant wireless access.

What could I do? I am puzzled... Thanks in advance for any advice!

Thanks for replyin'...

It's a MacBook Pro 15" Retina, running Windows via bootcamp. To control my "herd" of PCs (they run simulations), I've always used such laptops for Windows machines and had no issues. The "Disable on wired connected" option is disabled and always was. Only after that router change and Windows update, the whole shebang no longer works : (

Can't be an Apple issue though, as the laptop is running Windows 7 Enterprise natively. Symptom is the same on other laptop.

The only thing that was physically changed in the network is the router. The only software change was upgrading Windows 7 Enterprise.

Bump.

Someone's got any ideas? Where in Windows 7 can one check/analyse why both ethernet and WLAN are not working in parallel, as they used to? What could be in conflict here?