When building the castor on your own under windows with the directory hierarchy including directories with spaces in their names, building fails as some java code does not get generated. The error will look like 'Unknown protocol c' (in my case sources were lying under the Desktop, full path C:\Documents and Settings\mweber\Desktop\trunk) and finding the mapping file will fail – thus the generation of the java source code from the respective schemas does not work or not work as expected, leaving you with unresolvable symbols 'FieldMapping, 'ClassMapping' et al. A workaround for this is to put the castor source code under a directory which does not contain spaces.