The network in the labs has always been a bit flaky. I think there are a variety of issues here, such as faulty cabling in the labs (think C16 and transfer speed being half the going rate) and perhaps ACL issues on the switch.
I've made a request at the Helpdesk to look in to our own VLAN with our own ACLs etc. but I'll also need to track down the other problems. Task coming in next.