I get the same problem ("unable to determine ValueType for Class"), having upgraded from WebSphere 6.0.1.21 to 6.0.1.23 (which includes an SDK upgrade to 1.5 SR9). I'm running on Windows Server 2003, so don't think it's platform related. Did either of you manage to find a fix for the problem? Thanks in anticipation! John Fa wrote: -- View this message in context: http://www.nabble.com/unable-to-determine-value-type-class--***-URGENT***... Sent from the drools - user mailing list archive at Nabble.com.