Just had the same issue crop up. I just read the spec sheet for the LM1973, the volume controller inside the sub, and it defaults to mute on power up. So if volume change messages aren't being received for whatever reason (failed microncontroller in dock, bad cable, noise, etc..), you won't get sound. The controller takes a serial stream of 8 bits to select the channel and 8 bits to set the attenuation level. More than half of the bit combinations for attenuation level result in a muting action. Only the last 3 bits of the 8 used to set the channel are used, the others are always 0's, since the chip only supports 3 channels. These channels are used for left, right, and sub. Normally the dock sets the left and right channels to the same levels at the same time, but noise could cause their levels to get set independently.
If the dock connector's clock and data lines go straight to the LM1973 chip somebody could probably make a circuit to control volume by sending the right 16 bit values. It could be simple and just set the volume on all 3 channels to max, or support ramping up. One problem might be that the custom microcontroller code in the original dock might be curving the volume up differently for the sub vs. the satellites, throwing off the original balance. Still better than nothing. If replacement docks continue to fail someone might find it worth their while to make and sell such a volume level setting "adapter" to skip the dock all together.
Lastly, I am reading that the docks were no longer for sale for a while and then recently brought back, does that mean these docks may have bug fixes that prevent future failures? I'd gladly pay for a reliable dock. Like a lot of people have said already, no one has made a better 2.1 set since these came out. Klipsch - why don't you update this set and re-release it, either excluding the dock or fixing the reliability issues, while keeping the Class-D amplification and the RSX-3's. Isn't it nice to be the class leader?
These speakers bring you a lot of cred, exposing the brand to a level/segment of customer that is less likely to be familiar with the brand. I have recommended the ifi set to several people and many of their friends that were surprised by the sound of these "computer speakers" now know and remember Klipsch name. These are people that find buying amplifiers and speakers by component too cumbersome to delve into, but can still appreciate the extra quality the the ifi brings over the existing promedias and high end logitechs. It makes the cost benefit of the brand clear, at a less risky price point, in a way the promedias can't. The dock is useful in getting these customers so I'd suggest including it, but working out the kinks first.
I'm keeping my fingers crossed that someone comes up with a long term fix for this. Also, if anyone has experienced reliability issues w/ the docks just recently being sold, please speak up.