Outlook "disconnected" message after network change.

Hi,

I'm looking for help with Outlook with bounded exchange account. We got configured some VLAN's in office, when employee goes to conference room (another VLAN, another IP) for example and come back to his workplace Outlook can't connect to exchange server and it says "disconnected". WEB Outlook works perfect. Employee has to restart his pc to make it works again in desktop Outlook.