Thanks to Michael Tsang and Ramesh Viswanathan for tipping me off this weekend to two new issues with post-SP3 hotfixes for Windows NT 4.0.
First, the "simptcp-fix" denial of service attack has been temporarily removed while a reported problem is investigated. The FTP site includes a note requesting that users check back later for a newer fix.
Also, Microsoft has released a new hot-fix which fixes the issue with flooding a WINS server by sending UDP 13 packets to it. This hot-fix is available on the Microsoft FTP site