Sometimes this happens to me.
You can get around it simply by assigning a permanent address on your router to the MAC (hardware) address of your computer - this should be possible in the DHCP settings screens, using information available from the router once your connection is established.
Then you can permanently assign an address on the machine itself on the connection settings.
That way whether you use DHCP or allow the hardware address to be permanently set, you will always be using the same address and no other device will take it.
Its not ideal but it will definitely fix the problem.
BW