It sounds like something going on with the WiFi, perhaps wireless interference. I would suggest opening up command prompt and running ipconfig /release then ipconfig /renew, that will reset your network adapter.
If you continue to have issues, and it's at work only, assuming you aren't the network administrator, contact them, see if they can take a look if it's something on their side.
Also, are you using WiFi, or is it a direct ethernet connection?