Please check the messages in "Runtime Messages" below the preview area of the layout editor. There you should get more information.
For development purpose define the logging as follows: open Configuration > Logging in the tools. Define in the editor:
Code:
<logging level="INFO"
console="true"
outputclassmethod="false">
<loglevelmissingpropertyget level="INFO" stacktrace="true"/>
</logging>
You then receive a stacktrace in the console and in the log.
Logs are in tomcat/work/Catalina/localhost/<yourapp>/
Kind regards! Björn