They could have blocked your MAC address or there's something interfering with the wi-fi signal itself, something using the same freq as the channel the wi-fi router/ap is on.
Quite frankly, if this is a wi-fi setup for internal use only and it's NOT requiring encrypted VPN with MAC-address filtering and username/password login via RADIUS on a WPA2-enabled access point or router then I would question the sanity and security credentials of your IT staff.