I just fried two HP-41s?

[BartDB]

It's not uncommon for multiple sets of batteries to have a bad cell. Take all the cells out and measure them individually. Throw out any that measure 0V (short circuit) or random readings (open circuit). Anything 0.8V or above is usually salvageable.

Also check your multimeter leads. Put it on low ohm scale and short the tips, you should get a reading of <0.5ohm. Random readings indicate bad leads (has happened often enough with mine that I always have a spare set).