Java Unsupported major.minor version 49.0 - where is it coming from?

I have downloaded the zxing Google QR code from SVN and used eclipse to edit one of the class files.

I've compiled the changes using ANT and it runs fine locally. When I run it on alive server I get an error:

500 com/google/zxing/client/j2se/MatrixToImageWriter (Unsupported major.minor version 49.0)
com/google/zxing/client/j2se/MatrixToImageWriter (Unsupported major.minor version 49.0)

I have tried compiling it in JDK 1.6 and 1.5 and I get the same error message. Is this something to 开发者_如何学Pythondo with editing the class file in eclipse, and eclipse saving it using a different JVM?

Live server is running 6.0.150

49.0 is Java 1.5, so it sounds like your server is expecting Java 1.4.