Hudson Build failed - It is not recognizing the jar added in class-path.

I am using the xmlunit jar to compare two xml files.
The xmlunit jar is suitably added in the build path (from eclipse) and the same is reflected in the .classpath (A new entry with a <classpathentry> tag)
My code is running fine in eclipse.

we have an exclusive Hudson job to take care of the continuous integration. The hudson refers to a predefined source repository and the source repository contains the classpath with xmlunit classpathentry. However, whn i give a build at Hudson, it always get failed. And showing the error " import org.custommonkey.xmlunit.* " is not resolved.
It is not recognizing the jar.
Can anyone please help me out..

Thanks in advance.