Well, I went on a hunch and replaced the mswsock.dll in the C:\WINDOWS\system32 with the one from the C:\WINDOWS\$NtServicePackUninstall$ directory, which should be the one previous to XP SP 2 installation. This worked for a little while, but also failed with the same dam DNS error.
Will this never end? How could such an error be allowed to escape testing? Dam Mickeysoft!
Thanks goodness that I have an old trusty Windows 2000 installation to fall back on, otherwise I'd be completely out of business.