A strange "Aw sh*t!!" moment...

I'm still scratching my chin on this. I burned up a perfectly good multimeter tonight while trying to read the frequency output from an old Miller DialArc HF welding machine. With the machine set to weld AC without the high frequency switch turned on, i read a nice, steady 60 HZ output, as would be expected. I turned on the high freq and tried to read the output with my meter, and fried the meter faster than i could yell "oh sh*T!!". Have no idea what happened. The meter was set correctly. Open circuit voltage should have been about 90 volts. I'm not sure what the frequency would have/should have been. Ticked me off to fry a perfectly good meter. Now i've expanded my "wonder what the output frequency is?" question to include "wonder why that little exercise just fried my meter?". Any guesses?

Edit: I know this isn't related to wiring, per se. I am a pretty experienced electrician. I am licensed. I'm not a dummy. Please don't bash me to badly if the answer to this question is obvious.