backup through Java

Folks,
I know this isn't technically a JDBC question because backup isn't done through JDBC, but I thought this is where the Java experts would be.

I've got a Java application developed in Eclipse interfacing a PostgreSQL 8.2.1 database. The user can do a backup using pg-dump.exe - the Java code invokes this as an external process in a thread (Jobs interface, in Eclipse parlance). This works some of the time - but not always. Since it works sometimes, I think the Java code that invokes pg_dump.exe is basically OK, but since it hangs at other times, there is obviously something bad going on. I don't know where to start looking for problems. I was wondering if anyone had seen similar behavior (Java is usually pretty predictable in my experience) or had some thoughts on where the problem could lie so I could at least begin debugging my app.

Thanks!
Michael Schmidt