@burnout426 Actually, after I responded to you, I reinstalled AVG Antivirus and as soon as that happened, the problem of bookmarks not saving or changing started back up. The 2 AVG files that LockHunter said were blocking modifications reappeared after I reinstalled AVG. I did that trick I mentioned earlier but with the Default sub-folder of roaming Opera Stable this time and that started things back up.
I'll probably wait a week until reinstalling AVG to see if the problem's gone away. I'm at a loss, for AVG hasn't given me this problem before. Did I do something in AVG to cause this? I hope it isn't a permanent bug, since my family bought it and it's useful in protecting our computers.