Technotrend S2-3200 unexplainable reception problems?

The other day I was about to watch the new german Rommel TV-Movie on ARD, Germany's first public tv channel. I wanted to use my rather old DVB-S2 PCI card, a Technotrend S2-3200, with DVBViewer, but most channels were showing a lot of pixelation and cracky audio. Some more than others: it looked just like the quality of the signal from my dish had suddenly dropped. Dish orientation was ok (it never needed to reposition it since it was installed in 1994). I checked the cable connectors, recutting the stub: no result. I tried with another stand alone receiver connecting to the same cable drop: perfect picture, the signal quality bar well above 75%.
Going back to the S2-3200, I tried upgrading DVBViewer Pro, tried upgrading the MPEG/H.264 codecs. No result.  Tried even a couple of other DVB softwares. No result.
Eventually I watched 'Rommel' with the stand alone receiver: I thought that the analog stage in the S2-3200 had developed some problems, and started looking for a replacement on the net.
Then I rememembered that a few days earlier I had changed the DDR speed in the BIOS to check for a possible compatibility problems. I rebooted and set it to 'Auto': perfect picture again on the S2-3200.
The funny thing is not the necessity of using the 'Auto' setting, it's that it just looked like a low quality signal problem, visually. If somebody is experiencing the same problem and is looking for an answer googling, I hope this post will be of some help.
Oh, and the (rather good) Rommel movie looks just like a (albeit partial) rip off of 'The Trail of the Fox' by David Irving. The influence of that book on the screenplay is rather obvious.