This isn't strictly a programming question, but it is Java-related and is getting in the way of my programming.

I'm using Windows Vista with the jdk1.6.0_07 and often after I've built my latest jar file (using a batch script) the program doesn't start. I have tried double-clicking it and launching it from the command line with several versions of Java.

Sometimes even after rebooting the computer my program won't start, and I have to reboot again. Today, though, I tried loading a Java applet and not only did it work, my program also loaded the next time I tried it.

Has anyone had this problem or knows what to do?

There isn't much to say based on what you tell as it lacks all details. What about paths? Where do you store your apps? Is that applet that your ran succesfully in the same location as the other ones, did it work before or not, which classes does it use, etc. et.
Until these things are known, it's anyone's guess what could be wrong.

Not sure about this issue, but what I would do is run the non-jar program under a console, and see what type of errors it spits out.