Well, Ant is a Java application, so you could debug it via an IDE as you might any application.
More normally the way to fix Ant problems is to run it with the -verbose or -debug flag. That will give you pretty detailed logging of what is happening.
Originally posted by Tim West: If you haven't already upgraded to Eclipse 3.1, I'd suggest you do so - Ant integration is considerably improved since 3.0.
-Tim
However, use of the -verbose flag is possible even under Eclipse 3.0.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.