I ocassionally got the same thing too! Still don't know what causes it.
Most of the time a programs works fine, but suddenlly it returns this
message (probably after a did something, but I can't recall).
I thought that's my machine's problem, Now I think it might not be that
simple.
BTW, I have
Your CLASSPATH environmental variable must be set to point at the root
directory containing your class files. So, in this example, if your
current working directory was /home/Ozer, then you need to set your
CLASSPATH like this (assuming you are using the bash shell)
export CLASSPATH=$CLASSPATH:/
