If you are trying to reject an asset that has been sent to you for approval and you get an error page containing the following message (or similar - the important part is "Component Exception occurred whilst getting processor AssetRejectedProcessor"):
... then the error is probably being caused by the workflows.xml file that your Asset Bank is using being designed for an earlier version of Asset Bank than the one that you are running.
How to fix
Find out what version of Asset Bank you are running (use the About Asset Bank link in the bottom of the page - this link can be disabled, if so go to http://<your-asset-bank/action/viewAbout).
Request the workflows-default.xml file for your version of Asset Bank from the Asset Bank support team.
If your existing workflows.xml file is customised, make the corresponding customisations to the new workflows-default.xml file.
Rename the file to workflows.xml and copy it to [TOMCAT_HOME]/webapps/asset-bank/WEB-INF/manager-config/workflows/ on your Asset Bank server, overwriting the existing file.
Restart Asset Bank (usually by restarting Tomcat).