This error happens on servers that do not have the proper library support in place to handle Multi-Byte Character Strings.  By default, Jamroom attempts to use UTF-8 encoding/decoding for HTML character entities that it displays, but on some servers, you will get this error in your PHP Error Log.  The solution is to:

• Log in to Jamroom as the Master Admin.
• Click on the Jamroom Config link, and select the "Environment Options" link from the menu.
• Set the Entity Encoding drop-down setting to "ISO-8859-1".
• Save the settings by clicking on the "Update Settings" button at the bottom of the page.

That's it - you can clear your PHP Error Log and you should be good to go