I was finally able to “fix” my phone by doing a factory reset. Once I did that, everything installed and updated without any problems. Of course, then I needed to re-install all of my apps and data, since a factory reset wipes out all the data, including the virtual SD card. To make sure I didn’t lose anything, I also needed to backup and restore everything on the card to my computer. The entire process was a gigantic nuisance. It really shouldn’t be that hard to keep your data.