What did I do?

This morning, working in a large text document, I realized that all of a sudden all the upper case characters had been converted to lowercase. It seems I accidentally issued a command that has that effect. I believe at the time I had caps-lock on, had forgotten that, and issued a commonly-used command, probably a motion command, with it in effect. Fortunately I had saved recently and was able to recover most of the file from backup.

What did I do? 

Thanks,

------------------------------------------------------------------------------------------
Eric Weir

"Uncertainty is an uncomfortable position, 

but certainty is an absurd one."
 

- Voltaire