Seems like people have successfully used the last several firmware versions: 1.20.06, 1.32.01*, 1.40.06. I'm still on 1.32.01 as I have no real need to switch to 1.40.06 and wrt PCs and electronic gear and such I generally subscribe to the "if it ain't broke, don't fix it" theory.
* My NJB3 lists it as 1.32.01, but the documentation I've seen online all refers to 1.32.02. Not sure what's going on there.