Okay. So even though it is a slightly different pattern (e.g. my problem is consequent and can be semi-solved consequently) it could indicate a bug in the firmware, which causes some drives to not being recognized (incl. some of WD's own).
But what causes the communication fail between certain drives and the TV LIVE is a hard to tell. If it is just random which drives work or doesn't work it is a major bug, because the consumer wound't really know which HDD to buy.
I am hoping to hear from others with similar problem or the like. Also if anyone have an idea of how to get a little deeper into the problem please tell.
Perhaps a firmware downgrade could lead to something. But is this even possible?
@jago_ and Totof13: What file system are you using?