cdo corrupts attachment

I just started getting this with the last w2000 server update.

I have an asp page that uses cdo to email a file. It has worked correctly for months, now all of a sudden it corrupts the file. I have checked the firewall, permissions, attachment checking software, etc. I can use the same code in VB6 and it works fine, it's just from the asp page that the attachment gets corrupted. Any ideas?