Hi there
several possibilities here
1) Does your router assign IP addresses via DHCP -- usually works fine but very seldomly you might have another piece of equipment that wants the same IP address -- reset the router and re-boou all machines.
2) switch to BRIDGED networking rather than NAT - this will use another IP address but if you are at home that shouldn't be a problem.
3) Assign a specific IP address and Gateway when setting up the network connection (only do as a last resort).
BTW ensure your firewall allows vmplayer as a permitted program and that you haven't got any AV software hosing everything up -- McAfee (Or better known as Mc AWEFUL) usually hoses anything and everything up.
Use also the latest version of VMware player.
(Note also if you are in a Hotel / College / Bar / Other public place you might find when using a Wifi connection all the IP addresses have been assigned -- there's then nothing you can do in this case until somebody logs off).
Cheers
jimbo