Ralf,

Those messages indicate files corrupted, possibly by errors on transfer or action by anti-virus software or similar.
I thought files should be re-sent in such circumstances but it may depend on when error is detected.
Suggest try re-boot then reset project if issue persists (set "no new work" and drain workunits first).
May also be over-heating or failing memory.

Paul.

And why are similar errors now start to show up on a whole bunch of other hosts as well, all which are otherwise crunching along just fine?
Well, MIP uses memory heavily. I know that if you are running MIP exclusively, there will be an inordinate number of cache misses. ( This information comes to me from someone much more knowledgeable on computer architecture than I am.) If other projects ahve a smaller or less intensive use of memory, doing the reboot will reset any locked up memory locations.There may be some other reason that particular host is throwing errors only for the MIP project, but it is beyond my range of knowledge. (Heat, dust bunnies, transient voltage fluctuations, etc.)
Good luck
Cheers