I used to up in a similar way. But, I found in the end, it is just easiest to install the whole thing on the data drive. It keeps this type of error from occurring.
First thing I would do would be to go the folder which contains the SQL databases that you are able to access as a domain admin. Go to the AmazingCharts.xml file and open with Notepad or Wordpad and make note of the path it has for the SQL Server databases. Also make sure that the folder that does NOT have the databases it in it does NOT have an AmazingCharts.xml file. If so, just rename it to .old.
Do you find that the mapped drives work better? Have you tried giving the domain users full control on both the shares and the permissions. We can always work backwards, taking everything out of the equation. Firewall, permissions, shares. Also, how do you have the inherited permissions set up? By default, they should both be unchecked, so it is probably correct.
Domain users have access to all shares they are given rights to on that user domain. Authenticated users are can access those shares plus available shares on all other trusted domains. I doubt it is an issue.
Given that it is Sunday, if the issue is still not fixed by Monday morning, the easy way out is to make everyone domain admins. I know... But, at least you know that anything they do to screw things up would be accidental, and to be honest, we screw more things up on purpose than they do accidentally.
