Wally,
My guess is that you have one of three possible problems.
1. Speaker wire is shorted. I suggest removing all of you speaker wires from the binding post on the receiver and check them to make sure a frayed wire is not touching another wire or another binding post. Check at the speaker end also. You can try connecting only the front L&R speaker first and see if you still have the problem. Then connect the center and check, then the surrounds and check again.
2. Your speaker impedance is too low and your amp can't deliver enough current into the speaker load you are using. Speakers are generally 4-8 ohm nominal impedence. Most amps work OK with these unless you connect two speakers to the same binding post which cuts the impedance in half. Most receivers don't like impedences less than 4 ohm, so this may be the problem. Additionally, if your amp has A&B main speaker connections, you probably shouldn't use 4 ohm speakers as the amp will see them as 2 ohm if you play both at the same time.
3. Your receiver is broken. Call the dealer you bought it from. If an individual, ask them for assistance.
That's my $.02 worth. I hope it helps.
TIC