My right posterior deltoid and lat are messed up somehow (suspect I went overkill on my last workout's DB rows). They don't hurt at all unless I try a pullup or some other means of significantly engaging said muscles.

What type of injury does this indicate? And how long should I wait until I resume training these muscles?

Could be a rotator cuff injury in your shoulder. The rotator cuffs are the most prone to injury out of any of the muscles in your shoulders.

In your lat you might have overstretched/pulled it somehow.
Both of the above will be due to bad form, overtraining, or just plain bad luck.

Wait until the pain is fully gone before doing anymore strenuous exercise for you upper back and shoulders.