Thank you for the quick reply. I read through that "dummies" post and completely missed that post. I specifically remember seeing the one right after it, too, so now I feel silly about that. With regard to the fix suggested in the post you linked, I checked my firewall just to be sure, and the entire IP range of 192.168.0.1-192.168.0.255 (My PS3 is on 192.168.0.105) is in the "trusted zone," so I don't believe it's a firewall issue.
However, the way I wrote that in my first post was misleading, and my mistake. While I did recently reload my SSD, that's actually irrelevant to this issue. I reloaded my SSD two days ago, and PMS worked normally (the old way) since then. This morning, I uninstalled and reinstalled ONLY PMS, to move it to a different installation location on my computer. After that reinstallation, I'm getting the described behavior. The only thing that changed was the installation location of PMS; no network, software, or infrastructure changes took place. Literally the only thing that changed was the removal & reinstallation of PMS. Any other ideas?