Based on my problems with dialup, when Qtopia has corrupted various networking files by adding Wifi or DHPCD stuff to them, making me unable to get online, also check the contents of the Network.conf file.
/home/zaurus/Settings/Network.conf
If all your config and settings files look okay, reboot. Sometimes networking is done with info in a hidden cache and you may have to do a soft reset to find them. I'll be adding another blog post about this when I feel up to tackling Wordpress' incompatibility with Opera...check my blog in a few weeks if you want to see my experiences with corrupt network settings, in two separate posts that are not quite completed.
Oh, for early ROMs, it may be in /home/root/Settings/Network.conf
sdjf