Found this zombie-late thread answer over at http://dev.fullxml.com/forums which should cure dickdutch.com’s recent affliction with said warning.

lharbin Posted - 01/31/2005 : 19:53:00
The error is caused by a permissions issue with some folders inside the wwwroot folder. It has been a couple of years since I set mine up, but I do remember it took some time before I got it right. It seems like I had to allow write permissions to the db directory for I_USR.

pbshaver Posted - 08/07/2005 : 19:45:39
> quote:Originally posted by lharbin
> …It seems like I had to allow write permissions to the db directory for I_USR.
This fixed two problems, one the “You must install…” problem and also fixed access issue where no account was allowed to login. Thanks

miedema Posted - 07/20/2006 : 01:11:13
I also had this problem a number of times and it has to do with permissions.

With the new backup module the problem is easily fixed.
Just delete data.xml and rename data.xml.tmp to data.xml and the message has gone.

So - it’s officially a permissions deal :. bumping it upline