Please see this thread - http://www.nabble.com/Bug-in-IndexedParamUrlCodingStrategy-1.3-Beta3-tf4440109.html#a12669595 .
The issue is when ever i use the IndexParamUrlCodingStrategy on a page that contains a Stateless form, the following error occurs:
[RequestCycle] Not all parameters were encoded. Make sure all parameter names are integers in consecutive order starting with zero. Current parameter names are: [wicket:interface]
org.apache.wicket.WicketRuntimeException: Not all parameters were encoded. Make sure all parameter names are integers in consecutive order
The issue seems to be that the pagemap is null and the Map parameters that are passed are not able to be parsed.