May be another sign of broken network is new problems accessing ftp service, it suddenly after coonecting hangs on LISTing files / getting data and just passive mode solves it (before it worked w/o passive mode 100%).
I am quite sure first time I get this trouble after installation of CDMA modem driver but I already unninstalled it.
I uninstalled also all network adapters, restarted, manually cleared registry and installed it again from scratch, but this still occurs.
Sometimes ipconfig reply with "zero configuration" just promt c:\ is displayed, no adapter listed.
I tried install SP2 but this don't solved it (and using SP2 now).
I also tried to fix winsocks corruption by entering "netsh winsock reset" and reset IP stack by "netsh int ip reset" but this doesn't help. I used to switch network settings before using netsh -f (pushd interface ip) to home/work as alternate configuration doesn't work for me well - it didn't set gateway right.
I also tried to reinstall Computer Browser and Workstation services - no success.
I hope I have not forget to write anything important.