Because it obviously ISN'T the building's WIFI.
If it works with previous OS X and other machines, then there is some sort of issue with the OS X wireless networking software.
I haven't seen any issues like this, but I only have Cisco and Apple wireless gear.
So it works with previous OSX, other machines, phones etc, but your current version of OSX works with your home WIFI...
What part of this is telling you that OSX is broken? It's obviously a bug between the authentication used on the buildings WIFI that you're not using at home! That doesn't mean that OSX is broken... get the IT dept to update their firmware?