Blurred when moving could be because its an 'interlaced' image
http://en.wikipedia.org/wiki/Deinterlacing

Try selectig the 'de-interlace' button on the video input window to see if that helps.

Blur would be seperate from lag/delay.

The decklink cards inherently frame buffer as they are designed for NLE rather than live input (this is why Active Siicon cards are better)
There is no way to turn off the buffering - try a lower resolution and see if that makes a difference. (720p if possible)
It usually happens when the PCI bus is busy as HD-SDI capture takes a lot of bandwidth compared to SD.

What other cards do you have installed?
What hardware version is your mac?

S