Avira "Deny Access" empties parent folder

Avira "Deny Access" and an empty parent folder

I've never posted before and don't like to show ignorance, but since I couldn't find a specific remedy after extensive googling, maybe this will save someone else hours of fear and frustration.

I was using the free trial Avira AV on my old Dell (with XP-SP2) and having conflicts with Sunbelt FW for updates. I hadn't updated the AV for a couple weeks. I finally accomplished a manual update (it was a relatively large file) and shortly after ran an updated MBAM scan. During the 8-hour scan, Avira (coincidentally?) came up with four hits of "infected," 7-yr old pdfs stored on various drives, including my working folder and backups. The default (if memory serves, which it doesn't always) action was "deny access." Normally I'd first try "quarantine," but the "infected" files were old and dispensable. I didn't see any obvious reason to not follow through, but on a whim I changed the fourth action to "rename file." Both options seemed less dicey than the choice of "delete file."

Later, I discovered that 8 years worth of files were "disappeared" from my working folder, which had contained copies of the "access denied" files. The backups were gone, too. The parent folder properties indicated, "Empty" and "0kb" size. I searched everywhere for the missing files but found only a backup from two years ago on the second of three drives -- the location of the "renamed" file. No mysterious zips or large files came up in searches by date (searching system/hidden, too). The four files in question weren't on the Avira quarantine list.

Like I said, I couldn't find much on various forums, except that evidently when Avira "denies access" to a file, it very thoroughly denies access to parent folders and their files, too. And there's no "undo" button. Unfortunately, the few forum threads I found were all about "How do I delete the infected file if I can't find it?" rather than, "How do I get my files back?"

Clearly, I'm no techno-guru. I still don't understand how "deny access" works. It was pretty scary to finally try uninstalling Avira. (Would my files go down with the ship?) After the uninstall, I could access an external drive, 10-month old backup with the files in question, but not the active folder. Then I uninstalled the FW. Voila. The active (parent) folder was repopulated or made visible or whatever. (Could be nothing to do with the FW -- maybe another reboot would have done it.)

I tested the "infected" files on Jotti and all turned out to be false positives detected by the Avira AV Guard.

Superstitiously, I did not reinstall Avira (in case some ghost-registry entries re-disappeared the files). I'm now trying out Avast free AV and Comodo 100%-free FW (with inactive Defense+). Paid-up Trojan Hunter has been running since before they started charging for it. Spyware Guard and paid-up WinPatrol are always running, too. I use multiple scanners at sporadic intervals: MBAM, SuperAntispyware, Spybot SD, AdAware, etc., and various online scanners. Perfect Uninstaller and WinASO RegOpt to clear out the crud. And I drool over MacBook Pros, which require relatively minimal security software and scan-hours.

Undoubtedly there are gurus out there who can explain or clarify misconceptions I may have laid out here. I don't want to slight Avira or Sunbelt, especially since it's possible that I inadvertently caused AND solved the problem without recognizing issues unrelated to security software. But maybe the simple solution will help (and reassure) other techno-nots. Certainly it's yet another wake-up call to back up files more often -- preferably on an external drive that I can unplug between backups.