Thanks to Michael Tsang Kwong Yiu for the tip: Microsoft this week released two new hot-fixes for Windows NT 4.0 Service Pack 3. The first, called the "2G Crash fix," corrects errors in systems where RAM exceeds 1.7 GB (I'm guessing most people won't need to worry about this one. It can be found on the Microsoft FTP site.
The second fix, is an updated fix for the denial of service attack against Windows NT Simple TCP/IP services. You can find the new version of this hot-fix on the Microsoft FTP site as well