In some cases, you may need to know why a particular java applet (Data Mapper or Process Flow Designer) is failing. If the message you're receiving doesn't provide enough information, you'll need to enable the Java Console Mode.
1) Go to Control Panel > Java
2) Select the Advanced tab
3) Expand the Java console entry > Select Show console > OK
4) Go back to Adeptia and try and launch the applet again
5) A window will appear providing the logs for the error