The server says an activity class is unknown
This error may be manifested in the server logs as follows:
#1185805812851:2# A problem has occurred during request processing. #1185805812851:2# There was a problem creating the activity instance (activity name uk.org.ogsadai.ListDirectory, instance name uk.org.ogsadai.ListDirectory-ogsadai-1141788bcad). #1185805812851:2# java.lang.ClassNotFoundException: uk.org.ogsadai.activity.file.ListDirectoryActivityXXX
This means that the activity configuration specifies an activity class name that does not exist or cannot be found by the OGSA-DAI server.