IP config with MN-700

Hi,
I have a MN-700 router connected with 2 desktops, one
running XP (via ethernet cable) and another running 98
(wireless pci card), both connect really well to the MN-
700. Now I'm trying to connect a laptop (Dell latitude
D800 + True Mobile 1400 Mini-pci card) and for some
reason the connection won't work unless I assign a static
IP to it (192.168.2.2) and change the DHCP starting
address to 192.168.2.3. The problem is that I also use
this laptop to connect to my network at work, and in this
case I need to change TCP/IP back to obtain an IP address
automatically... what's strange is that my other 2
desktops are configured for automatic IP and I never had
a problem with them. Any help will be greatly
appreciated, I've been searching through this message
board for an answer but haven't found one yet.