Your router sounds messed up is all....have you checke the lease settings on the router? How long do you have the dhcp lease set to?

Also, is your setup use mac filters or no? If so, I assume you haven't changed any nics in either PC?

If it were me, I would download and install the latest firmware update for your router or cntact them about it.

You PC's (or dhcp whichever way ya wanna look at it) should request the same Ip it was using before, thats the nature of dhcp, however, if that ip is not available the dhcp server will TELL the client to use this one...usually incremented by 1 until a free IP is found.

EI: PC uses 192.168.1.1 after reboot that IP is not available so after dhcp from the PC request's it, the dhcp server will deliver a nack(no)and send the next available IP to your PC incremented by 1.

This is normal dhcp server behavior.

Try setting up both PC's statically and turn the dhcp server of the router off....test, if after a few days you have no troubles then you KNOW it is the routers dhcp server that is in error and therefore the router manufacturer must fix it. Yes?

Curiousity demands I ask what type of router it is?

Cheers,

J