Thank you for your replies, but both the TV and the HT-E5530 are not in demo mode and resetting unfortuately does not change anything in the behaviour of the HT-E5530.

I contacted the local Samsung support here in the Netherlands and the reply I got was also not satisfactory at all. Basically the advice was to try a reset and in case that wouldn't work, to contact their Dutch repair service. As far as I can tell, no action was taken to try to reproduce the issue.

Despite the fact I like the slim design, as well as the gloss finished speaker set, I will try to exchange the Samsung something else. The same firmware is shared by a number of samsung HT models, so I have no confidence in buying a higher end Samsung. Maybe I'll even go for a seperate A/V receiver set up.

There is also a thread here on CNET describing a bug that causes the audio sync delay to drift (increase with every reboot of the HT-E5530), which dissapears when 24fps is switched off. This also tells me that the firmware on the device is not functioning properly.