DON'T LAUGH AT ME.
Because you figured this out a long time ago. I'm a slow learner.
I finally found the magic formula for making chicken in a slow cooker. Well, at least boneless, skinless chicken breasts. And at least in my slow cooker.
Start with frozen chicken breasts.
One quart water (for 4 -8 chicken breast halves)
4 bouillon cubes (yea, I know they are salty - I do not keep the broth, although the frugal homemakers who DO NOT HAVE A WATER RETENTION PROBLEM would want to strain it and freeze it for future use)
Cook on high for 4 hours. (Just until the liquid starts to bubble in the cooker)
Remove chicken, cut up, shred, or leave whole (although pieces will fall apart if you are not careful)
Add favorite topping such as barbeque sauce, salsa, gravy, whatever.
Last night I shredded the meat, drained the liquid from the pot, threw the shredded chicken back in the pot, added salsa (heated first in the microwave) and shredded cheese. I kept it in there for just a few minutes until everything was gooey and it was ready for tortillas. My family ate it up. And the chicken stayed tender.
I know you are not supposed to be able to ruin meat cooked in a slow cooker, but I find that if it is in there too long, it immediately dries up when you remove it from the pot. At first it will look nice and juicy, but then, EVAPORATION, and poof, you have dry, stringy meat.
So I am thinking the key is the AS SOON AS THE LIQUID STARTS TO BUBBLE part.
Will try a pot roast soon to see if my theory is correct.