mmmm ok... i don't think this is a winsock issue- if the winsock registry entries are corrupted, then this tends to kill a connection completely. I have never seen winsock problems cause intermittent connections.
While the connection is working try logging onto
http://root:root@192.168.100.1/
Post back the power levels and SNR readings- it may be that something is dropping out of range, thus you are losing connection.
Also, when the connection drops, leave the modem powered on, and remove the coaxial cable from it. Then do ipconfig /renew again and see if you have an ip address- post back what it is.
And finally... if you have XP service pack 2, the winsock fix can be done by typing the following at a command line and then rebooting:
netsh winsock reset catalog
