rbframework.dylib$1212 error

Anyone seen or know what causes this, its a 64 web app running on OSX, 32 web app is fine though.

Unhandled RuntimeException
Message: The data could not be converted to text with this encoding.

Stack:
String_ToText
String.$ToText%y%s
_WebSupport.Join%s%A1ss
WebResponse._Render%s%o
WebSession._HandleEvent%%oso<_HTTPServer.HTTPRequestContext>
WebSession._HandleRequest%i8%oso<_HTTPServer.HTTPRequestContext>
WebApplication._HandleHTTPRequest%%oo<_HTTPServer.HTTPRequestContext>
_HTTPServer.HTTPRequestThread.Event_Run%%o<_HTTPServer.HTTPRequestThread>
rbframework.dylib$1212
rbframework.dylib$1007

wrong encoding on some string converted to text ?

Perhaps you accept a string of text and didn’t DefineEncoding() ?