When I came back from vacation I noticed the Apple remote was not working anymore with my Mac mini. Pressing the “menu” button did not trigger Front Row anymore.

I checked the remote itself against the Macbook to rule out low battery or the like – it worked. Hence, the problem had to be the mini. An article in the Apple support forum suggested resetting PRAM and NVRAM as described in article HT1379. I did and it helped.