First, double check that your classpath is indeed correct. 
Second, try opening the jar and check that it actually contains the org.apache.commons.logging.LogFactory class. 
Finally, try debugging by setting a breakpoint in the class loader. !!–Kolibri!!

If you're using maven for managing dependencies, add the following line in your pom.xml:

        commons-logging
        commons-logging
        1.1.1