Trouble at home

I'm running the trial version at home and at work with my laptop.  It hasn't given me any trouble at work where I'm on a LAN with a dedicated IP.  At home the network is wireless and it assigns an IP each time - usually one of 3.

I'm kind of new to this so let me know if I leave out any vital info to solving this.

I've got the laptop set up to be the secondary at work and at home.  It is running Vista Home Premium.  The primary computers (both work and home) are running WindowsXP. 

At home, Multiplicity SEEMS to be connecting because no errors pop up when I try to refresh the IP address, but the mouse just doesn't want to go over to the secondary machine.  I have VPN installed but Multiplicity doesn't work even after a fresh re-boot before I start the VPN.  What's strange though is that sometimes it works at home.  I just haven't been able to figure out what combination of settings are successful.  Any ideas?