The error "hexadecimal value 0x13, is an invalid character" is known to happen in DotNetPanel with Windows Server 2008 when web.config file has been modified incorrectly or completely replaced. This is because IIS 7 uses the web.config to store it's entire settings and any incorrect modifications or complete replacement to this file will cause the this error to happen
To resolve this please follow the below steps:
1. Make a note of all the virtual directories created for the website (virtual directory name and pointing path)
2. Remove the web.config file from the File Manager.
2. Delete the website from within DotNetPanel. (This will NOT delete any files of the website).
3. Re-add the website.
4. Setup all the virtual directories again.