all right...
first of all: I saved all the necessary data already (just when the message appeared the first time)
I tested it with powermax from Maxtor and it told me (installation confirmation tests):
smart attribute check: failure
all the other tests passed correctly...
Dunno what to do now... The Maxtor web site(knowledge base or something like that) doesn't have this error code/message and they therefore don't tell anything about this one...