Laptop -> Desktop OK. Desktop -> Laptop Funky

I don't remember when I first bought MP but it's been several years. Only problem I've had until now had to do with company network security policies (I'm a contractor so I've used MP on a number of different machine/protocol/net-hardware configurations -- also at home.) At my current assignment, I first installed MP on the laptop (actually, simply a function of having installed SD there first before I got a second machine). Later, the company gave me a desktop too and I installed it as the secondary machine. All worked well for a while but it was awkward when I didn't have the laptop, had to reboot it, or whatever. Because the laptop (sorry, in a docking station) was the primary, if it was out of the loop, I had no keyboard or mouse for the secondary. So, easy solution, swithch primary and secondary. Now, MP on the desktop as primary seems to drop the connection to the secondary laptop every couple of minutes and it takes a minute or two to reconnect. Both versions of MP the same, both machines running XP Professional with same service pack, etc. Oh, also, I could boot both lt and dt then use the lt to CTRL-ALT-DEL the dt to log in. Can't do that from DT; the laptop has to be booted and logged in before MP is active. Any advice appreciated.