First of all you could check that your host supports Frontpage and Frontpage databases.Secondly why did you not simply *publish* the website, when you do this many things happen but if you FTP you create a bog standard folder with nout special.
Thirdly I would look at the directory on the web-server and see how many databases you have. If the permissions on the directory are readonly then you will only be able to open it once and then the database will be placed in a locked state. You are simply trying to open more that one instance of the DB (feel free to correct me on this one spooky.
happy hunting
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Stuart Steele
StuWeb Productions 07808254916
http://www.stuweb.co.uk