On this MSDN blog: Troubleshooting HTTP 500.19 Errors in IIS 7 in scenario 8 for error code 0x80070005
(E_ACCESSDENIED
- General access denied error) it says:
Grant Read permission to the
IIS_IUSRS
group ....... the worker process identity (and/or the
IIS_IUSRS
group) needs at least Read access to the directory so that it can check for a web.config file in that directory.