dreamweaver "The parameter is incorrect" error (1 Viewer)

[swingkid]

hey

i have had to set up a site for a client using DW Templates.
They have the site now and are trying to update the Templates but they are getting an error on the Templates Pop UP box in DW

"The parameter is incorrect"

Anyone know how to fix this?
Got them to ininstall & reinstall DW but error still keeps coming up.

Thanks/Help