Okay, after some research I found out that a lot of very weird things have happened..
Please mind, that I am a complete Amiga OS noob..:
Seems parts of my OS installation went to my PCMCIA-CF card I use for transferring stuff. Usually this card is sticking in there, so I didn't notice this before.
And that card ceased to function, and took my whole system with it. Not only the Devs/monitors stuff, but a couple of other things as well.
Got most of it repaired now, but it took me quite some time...