That's along the lines I'm thinking. Something crashed or got corrupted differently than usual and is being stubborn about being erased. There may be a MTBF of millions or billions for such write operations that don't get caught and fixed while they happen, but they DO happen.
This type of problem comes from a faulty write operation. For some reason (usually a malicious program) changes a local variable and everything written based on that register is corrupted. It does not mean that you are infected, it just means that something happened. And believe it or not, it could possibly have been cosmic radiation impacting your hard drive and changing a single bit to screw you up. The Space Shuttle had that exact thing happen on one of its flights. Thats why we have backups.
Mark, do you recall the old IBM plugboards to setup the 5211 card punchers? what a nightmare! LOL
I should have been clearer. The cleaning I was referring to was for cached files, cookies and such associated with the browsers and internet. sometimes they won't clear if the program that made them is still running. Safe Mode changes the was read and write operations happen and could help and other cleaning programs would do it without ie or firefox running.
Yes, I remember the punch card readers. however when I got around to officially learning about computers and such they had just gone away. I was spared the agony. I had to deal with some lingering punch tape readers on industrial computers, but only long enough to eliminate them.
Mark