Thanks Rob,
I upgraded to build 22. Your perl -M command above does render the same error, which persists exactly the same. Any ideas where I can look for stuff? Is it talking about windows or about some lower level Perl code which does the threading? Is there a way I can know the right thread version for this OS?
I replaced errno.pm, no change.
This is a windows box, crazy things happen often.
Thanks again,
Craig.