... and landed on a board, which in turn ended up at my desk.
In production, it appeared to work OK and the device went through our testing procedure without any fault, until they attempted to reprogram the testing application with the final one. Hummm...
Closer insepction revealed that it is possible to reprogram it using ISP and if "empty" (erased, all FFs), also through the bootloader. However, reprogramming of already programmed FLASH through bootloader failed: bits which should've been changed from 1 to 0 were all changed; the other direction worked only here and there... An "all zeros" application could thus be programmed always, except that the usefulness of such application is questionable ;-)
Went to the "gems" box (a.k.a. thrash bin :-P )