The fix for issue
GROOVY-2515 broke the classpath options -cp and -classpath in startGroovy.bat. The options are still evaluated and the classpath is set correctly, but the options are no longer stripped from the command line but passed on to the starter main class. GroovyMain, for example, then finds the option -c in its command line and complains about the missing encoding:
The attached startGroovy.bat fixes this problem. However, I am afraid that it uses features of the set command that are only available in Windows NT and above.