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if you can't connect to your my sql database you won't be able to run xoops...
tell your host to open you a new one if the old one is problematic and reinstall - or backup the existing one via phpmy admin, import into new one and link XOOPS there by changing the mainfile.php, but WITHOUT doing any changes to the file structure at all...
if you are generally unable to connect on any MySQL database I think it's time thinking of a new hosting solution...