This is a very unusual and baffling error - the import doesn't care about the Build_Update def file. I have, however, encountered a similar problem (though not with Build_Update) with old versions of perl (5.004_04, not sure about later versions) with it reporting 'No such file or directory' for files that plainly exist. I traced down the problem and have fixed it for the next version.
What version of Perl are you using?
Jason Rhinelander
Gossamer Threads