After fiddling all night i found something out regarding the BMD cards.

We are using a Decklink standard and a Decklink extreme each in its own G5. We running two SDI feeds from the trucks. The Decklink standards can take both signals without any problems, while the Extreme can only take one of the signals properly. After talking with Black Magic for an hour, one of their engineers realized that because the Decklink standard has its connectors on the card itself, it is much less sensitive to bad signals, while since the decklink Extreme has an monster cable between, it makes the Extreme more sensitive. In this case a booster helped, or actually a scanconverter that has SDI in and Out. Everything is running smooth now.

Morale is: Cheapest card works best. If you do not need the Gen.lock functions, buy the Decklink standard.