you were exactly right
rechargeable alkalines didn't work, but the NIMH produce some vapor.
Thanks kina
(what's the reasoning here....Mah?)
I am sorry to contradict you guys, I am no expert, but i don't need to be one in this case

.
I am here sitting with my own magnum mod, checking every set of AAA batteries i have (eveready regulars, duracell alkalines, energizer alkalines, fuji regulars, several funky named unknown batteries that came with the flashlight and radio shark's own rechargeable Nickel-Metal)
And each and everyone gives me clouds of vapor, no detectable difference from Li-ions.
I do not know about how much they last, because i never use the 3 batt pack that comes with the flashlights. but they do work.
It just doesn't work for some reason when i mix types.
So the answer to your question happily is, your magnum should be working.
One thing I should add is that i believe in the electricity/electronic gnomes, strange things happen now and then even when everything is perfectly fine, i have owned a recording studio for 25 years and trust me...it happens more than i would like to believe.
Obviously 99% of the times it is us doing something wrong that is hard to detect, electrical connections can be really tricky.
What i always wondered is ...what about the other 1%?
I guess we will never have an answer for that hehehe.