Can someone explain the setting of threads

Hello,

I have a simple class with a main. I start my JSwat. I have a break 
point on the line where my new object is created. I click on the 'main' 
to set the thread.

What then. ? Ive tried Run To, Step Over, Step In and it just kills the 
VM. Its complaiing about my source file not being found.

Here is my set up.....

I have a folder called 'framework' which has the folders 
'com.myclasses.etc'. So this is set as the source path. My classpath has 
the usual jars that I need. The class name is com.abc.def.MyClass.

I get it to work sometimes. Othertimes it dont. What am I doing wrong ?