It doesn't necessarily mean either the woofer or receiver are bad. You could simply be over stressing the circuit. Woofers can draw a good deal of current when in use so it makes sense that unplugging it resolves the issue.
Have you compared the current draw of your old receiver to that of your new one? I would start there and then check the load at the breaker box to see if your sitting at the threshold. What model was your old receiver?
I would not jump to the assumption that either the woofer or the receiver are bad without checking the load at the breaker box.
Edit: looking at the manual for your receiver, it specifies that it only draws 240W (2A @ 120V) which isn't very much, but if you were at the edge of the breaker limit, you could put yourself over.