Examples of such issue:
com.caucho.jsp.JspParseException: _jsp/_logon__jsp.java:10: cannot
bad class file:
file has wrong version 50.0, should be 49.0
Please remove or make sure it appears in the correct subdirectory of the
This normally happens due to mismatch between your Runtime Java version and a certain library that was probably compiled with an older version of java.<!>
These types of bad class version errors are caused by a Java version mismatch between the compiled proxies and your run-time. Either try to change the Java version that you are running or try to find pre-compiled java libraries (where this error is occurring) that were compiled with the java version with which you are running the app.
Below are a list of some of the version numbers and their corresponding Java run-times, they should help you to determine that the classes with the libarary were compiled with what java version.
Version 50.0 = Java 1.6.x
Version 49.0 = Java 1.5.x
Version 48.0 = Java 1.4.x