On the plus side, as of last night whatever the problem was seems to have resolved itself. I had re-enabled Malicious Website Protection earlier in the day (to see if I could get it to provide an actual block message for you), and when I tried going to PSNProfiles it loaded properly. Not sure what the deal was, since I'd tried all the other things generally recommended (DNS Flush, empty cache, delete cookies, etc.), and turning off MWP was the only thing that finally allowed the page to load, BUT didn't record a block. Ah well, it's working now, thankfully. And I very much appreciate the time you took to try to help me figure out what was going on. Thanks again, xari.