The latest version of Malwarebytes has been released:
http://forums.malwarebytes.org/index.php?showtopic=108391
It was rather funny...When I opened the program to update the definition file, I saw on the inbuilt newsticker that the last version upgrade had been released end of January.
Me *muttering*: Hm, been a while since the last update...Isn't it time for a new one?...
Program: *downloads definition file...then proceeds to download file containing engine update*
Me:...Er...I was kidding... 
Anyway, no issues so far, and since it's the free on-demand version, it does not interfere with Norton :-)