Exception handling in the Remoting servlet transport should be modified so that it matches the behavior of the other transports.
This issue arose in support case 18171 (
https://na1.salesforce.com/50030000003iBdA). The fix has been applied in Remoting release 2.2.2.GA_CP01.
See
JBREM-813 "ServletServerInvoker should return an exception instead of just an error message"