what in the world just happened???

i've been working on a project - all of a sudden (it might have even happened WHILE IT WAS OPEN), every instrument in a different tuning defaulted to C. all of them. Bb clarinets, A clarinets, english horns, french horns - all in C tuning. I tried repeatedly to "replace instrument" - nothing. I'll click on what's supposed to be a Bb bass clarinet (that now just says "bass clarinet"... wtf???) and change it to "bass clarinet in A" just to try to get it to change - nothing. C tuning. I can't continue this project until this gets fixed. very frustrated