Windows NT 4.0 Service Pack 6A Breaks IP Forwarding

[zeio () IX NETCOM COM (Brendan Howes)]

While recently evaluating Windows NT 4.0 Service Pack 6A (Domestic
Encryption)  to fix the "non-administrators can't connect to Lotus Notes"
(and use AT&T VNC software) I discovered that Service Pack 6A breaks IP
forwarding from the RAS WAN interface to the Ethernet interface. I
attempted to use TinySoftware's Winroute 4.0 and 3.04a, both would complete
a dial to the ISP authenticate properly then either immediately hang up or
all IP operations would be interrupted. Sygate did work on Service Pack 6A.
An administrator at the ISP indicated to me that the TCP/IP protocol was
never initiated by my OS. Upon re-installing Service Pack 6, the problem
was corrected.

I believe this information is meritorious and should be passed on to make
it clear to Microsoft should take more time and consideration when
preparing service packs which provide fixes to many of the vulnerabilities
presented here. A more technical inspection of this issue is warranted.

Hardware/Software Problem Found On:
Windows NT 4.0 Service Pack 6 (6 and 6A)
TinySoftware WinRoute Pro 4.0, 4.1 and 3.04a
3COM EL3C905B-TX With  Driver el90xnd4.sys 3.50.40 / el90xbc4.sys 1.60.00.0000
x86 SMP (2 x Pentium II 450) / 256MB MEM
SuperMicro P6DGU (Dual Slot 1 GX Based, AMI BIOS, MPS 1.4)