Yep, running stock (4.3 OTA)...just rooted, that's all. My bad, I just realized I *can* use it as a phone when it's on USB...which seems not right, but maybe that's just what I was used to before--unable to use as phone when USB mounted (on my HTC). My family had told me they were getting weird messages when they'd try to call, during times I was on USB, and I assumed it was the USB mount when it was apparently something else.
But, the problem remains, I can't seem to have it NOT mounted as USB when it's plugged into my computer, or other device. And that seems to be what causes the microSD to get all fouled up. This phone is pretty new to me, and I didn't have any problems until I plugged the USB into the computer with a microSD card in it. My step-daughter has another Samsung phone (Exhibit, maybe??) and she says hers does the same thing when she plugs it into a computer.
I have always removed it from the computer properly, whenever there is an option for me to do so. Problem is, it will show up as mounted on the phone and computer (only the phone and not the card, if my phone thinks the card is unmounted), but I don't always get an unmount (or eject) prompt on my computer. And, the phone apparently doesn't have a way to do that manually, either. In those cases, I just turn off the phone before I unplug the USB. I thought that would be the best choice in that scenario...? Thanks for your feedback, I appreciate it.