16-bit error after updates

I have several Windows 2000 PCs that are experiencing the following problems
after users download some Critical Updates, perhaps SP4 or later.

Can’t run 16-bit Windows Program (This one also appears when I try to do a
clean install of SQL Anywhere after applying all of the Critical Updates)

And then they get a whole bunch of these error messages:

Insufficient memory to run this application

Quit one or more Window application and then try again

Then these keep coming up and the computer is essentially useless until you
hard reset. Sometimes you can stop the messages by killing the NTVDM process.

Have you seen this and do you know of a fix for it? I’m still scouring the
web looking for answers. Any help you can offer will be much appreciated.
Thanks.