sharing efs files between xp & vista

Hello,

I'm trying to share efs folders/files between an xp workstation and a vista
workstation. The files are in an external usb drive. Users from each
workstation have exchanged certificates as documented in:
http://windowshelp.microsoft.com/Win...c275b1033.mspx
(synopsis: I exported and imported pfx files between workstations)

My vista workstation can view files encrypted by my xp workstation.
However, the other way around does *not* work: my xp workstation cannot view
files encrypted by my vista workstation. How do I get this to work?

Thanks!

- vijay