Today I received the HTR-9900 set I ordered.
Sounds amazing.
After setting up eveything, I ran the SmartEQ with the microphone to set it up.
Eveything worked ok.
I started watching a movie after playing some minutes with some cds, dvds, etc.
About 10 minutes into the movie the woofer made a strange noise (*plop*) and stopped working.
It made a couple of more smaller plops and then stopped again.
I stopped the movie.
After 1 minute or so the subwoofer started to make noise by itself (movie was paused, no sound).
It started to make loud rumbling noises, somewhat like thunder.
It was very loud so I switched of the subwoofer via the power switch on the back.
I took the power of the whole set and waited 30 minutes or so.
I switched back on the set, but the woofer didn't work anymore.
I checked cables, but those are ok. I also tried to set the woofer to loudest and to 160hz.
I checked the settings to see if the subwoofer was set to "on".
I ran the SmartEQ again, this worked, but only with a very low sound from the woofer.
Barely audible. The SmartEQ results show that it couldn't detect the subwoofer, so it is now set to off.

The strange thing is that a friend of mine has bought the same set 3 weeks ago.
His set ran fine for a couple of weeks, but now he also has problems with the subwoofer.
It almost doesn't work, but his woofer from time to time makes some strnage *plop* nooise, seemingly unrelated to the movie/music that is playing at that time.

Is there anything we can try to make it work?
I would be surprised that two (high-end) Philips parts are breaking so quickly after purchase.

Another friend also received a HTR-9900 this week, but hasn't installed it yet.
Do you recommend testing my set with his woofer?

I bought the set via internet (new, official retailer) so if I need to return it will cost a lot of transport costs.