Here's a rule of thumb:
Only include work history on your resume that DIRECTLY relates to the position you are applying for.
Why do I say that? Because no recruiter or HR person wants to wade through EVERYTHING... you don't have to tell them about that McDonalds job you got when you were 16, or the summer job at Wal-Mart you got after your freshman year of college. Just tell them the experience you have that is relevant to what they're hiring you for.
Do I have anything to back that up? Other than having to wade through it myself as a recruiter... Ask a recruiter. Check out websites like CareerBuilder and Monster.com. They'll tell you.
How do you explain the void? Be honest in your interview. Working in a different field in that void? Tell them that.
Any situations to change my mind? Can't think of any.
