... after hours of frustration I realized that these items (the ones with visibility set to 1) had descriptions that ended in "..." (three periods - I actually wrote "loading..."). Apparently
"..." (three periods - I actually wrote "loading...").
Apparently these three dots were screwing up the CSV (or the way Magento reads the CSV). Remove the three dots and everything works!!!
I am writing this here on the off chance that someone else encounters this same issue.