You stated that you installed NT 4-SP 1, then the new ADSM client, then SP3.  I
had some trouble with our first go arounds with the new client as well.  It
turns out we just had a corrupted download.  Download a new copy, and start over
with your NT box.  Service Pack 4 is now available, I would install that as
well.  Get NT and SP3 or SP4 up and running first, then install your client.
The requirements state SP3 or higher, possibly installing the client before SP3
corrupts it even before you get started.  After our initial corrupted download,
we have installed approximately 12 NT SP4 clients with absolutely no trouble.
Good Luck.

Sean
stecker.sean AT orbital-lsg DOT com