another problem?

This is with community edition (sorry I switching between them to try and get something working - perhaps not the most intelligent response but still)
12.0.1 and 0.7.62 using fsc

12:34:04 Compilation completed with 2 errors and 0 warnings in 1 sec
12:35:05 Compilation completed with 1 error and 0 warnings in 1 sec
12:35:06 Scala project FSC (2.10.0-RC1)
         java.lang.NoClassDefFoundError: scala/reflect/io/Streamable$Bytes
         at java.lang.ClassLoader.defineClass1(Native Method)
         at java.lang.ClassLoader.defineClass(ClassLoader.java:791)
         at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
         at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
         at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
         at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
         at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
         at java.security.AccessController.doPrivileged(Native Method)
         at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
         at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
         at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
         at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
         at java.lang.Class.getDeclaredMethods0(Native Method)
         at java.lang.Class.privateGetDeclaredMethods(Class.java:2442)
         at java.lang.Class.getMethod0(Class.java:2685)
         at java.lang.Class.getMethod(Class.java:1620)
         at sun.launcher.LauncherHelper.getMainMethod(LauncherHelper.java:492)
         at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:484)
         Caused by: java.lang.ClassNotFoundException: scala.reflect.io.Streamable$Bytes
         at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
         at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
         at java.security.AccessController.doPrivileged(Native Method)
         at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
         at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
         at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
         at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
         ... 18 more
         Exception in thread "main"