UnsupportedClassVersionError means you have compiled it with a more recent version of Java (I think 49.0 means Java�5 or jdk1.5.0) and you are running it with an older version. If you are still using Java 1.4.2 you can upgrade to Java5 or Java6, or you can set a flag on javac which will create code compatible with J2SE1.4.
Joined: Sep 18, 2007
How to set flag on javac?
Joined: Oct 13, 2005
Go here, find the tool you want (javac), follow the links and look for the source and target options.