If a getS1TbxPixelSizes.class is not present then getS1TbxPixelSizes.java needs to be compiled. 

All the jar's in S1TBX_FOLDER/lib and S1TBX_FOLDER/modules should be on the build path together with S1TBX JRE.

The compilation has to be into JRE 1.6 as this is the version used by NEST at the moment.