Unfortunately, the issues you are experiencing are symptomatic of an internal hardware defect, meaning a faulty main/control board (preamp section) in the receiver unit, or a faulty power supply/amp output stage in the sub, though there are many possible failure points. This issue could be a manufacturing defect, but is also often caused by a power event (shock/surge, prolonged over/under voltage condition, etc).
This could also be the result of age related wear and tear, as a 2005 model, that type of failure wouldn’t be surprising.
There is one step you can take here, both as a possible fix, as well as a diagnostic evaluation
1) Unplug the power cord from the receiver unit, and disconnect the acoustimass module as well
2) Wait at least 1 hour (60+ Minutes)
3) Press and hold the power button (on the set, not the remote) for 60 seconds
4) Keep holding power button while plugging back in, and for another 60 seconds after. When plugging back in, go directly to the wall outlet, bypassing any power strips or surge protectors.
If this reset process does not work, it would unfortunately confirm an internal hardware failure.
This is something that would require repairs to correct; though in general these units are not built to be repaired. Parts are not available, and labor gets to be expensive. There are only a few places in the country that will work on these, and repairs will typically be in the $400+ range. With that in mind, you're probably better off replacing the system at this point, as you can get a new and updated system with a fresh warranty for less than you'd spend on repairs.
Depending how you’d like to proceed here, I can help with finding parts, finding a repair shop, or recommending replacement options. Just let me know.
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