The following steps leads to an error when displaying Endpoints under the NMR advanced screen.
1) start servicemix
2) start NMR example - features:install examples-nmr
3) verify that HelloWorld endpoint is listed in UI
4) stop NMR example - features:uninstall examples-nmr
5) when the example has stopped the following error appears "Failed to retieve table data. Error in retrieving lice data from agent"
In step 2 the nmr example I was using was a modifed version of the SMX nmr example with 10 endpoints and 20 threads.