Okay, this is now a multiple-repeat problem. All functionality of copy/cut - paste is essentially gone. It will hit-and-miss with a proper copy-paste, but not normally.
I'm trying this through both the standard right-click mouse command and the keyboard commands as well, to the same effect. Drag-and-drop capability remains functional and unaffected.
I've had no luck with help on any forums, so a few weeks back did a brute-force System Restore. That fixed it. Now? It's back again. I'm using Windows Vista and Firefox 8.0 (but the problem comes with any type of copy issue on any program).
Both this time and the last time, all spyware, malware and antivirus programs gave my system a clean bill of health. I wish that I could correlate it to something happening, but I can't. Additionally, my hardware seems to be in complete working order as evidenced by the fact that the System Restore solved the problem and a hardware scan says that it's okay. I just need to know what's happening with some kind of software glitch.
I used AVG Anti-Virus, MalwareBytes AntiMalware, Kaspersky Rootkit killer, IOBit Malware fighter (pro), and all says that everything is good.
Using Windows Vista, I did a CMD sfc /scannow that could not repair autochk.exe, msiexec.exe adn msiexec.exe.mui. I don't know if that has anything to do with it or not.
The best thing that I can say is that it happens while I'm using Firefox. I don't know what I'm doing or if it's because of it... but it seems to happen then, because it's not until I'm done and go to do something that I discover the malfunction. I haven't actually done enough hours of troubleshooting to confirm that or not.
I've never blurted this on a forum before but, please help!
Addition (10/21/11): I did complete system scans today with AVG, MBAM, SAS, IOBit and the Kaspersky VRT, all of which say my system is clean of everything save for 9 tracking cookies, which are now gone.
I know that via sfc /scannow, my autochk.exe, msiexec.exe.mui and msiexec.exe files are corrupt. For some reason, they could not be fixed in that scan. I've also seen other places that explorer.exe issues can be causing other problems that I'm seeing (sudden alert that explorer needs to shut down, blinks out, starts right up again without reboot necessary). Perhaps that needs fixing that would also assist with this issue?
I did try this fix for explorer.exe (Explorer corrupted/infected) but it didn't work. I also tried this (Brink's vistax64) to repair autochk.exe, but I can't seem to give myself enough permissions to write into the System32 folder no matter what I do.
Does any of this sound like it would exacerbate a copy/paste issue? The wonderful part is that thanks to Lenovo, I have no Vista discs to do any repair with, just some thorough full-system backups, a brute-force that I'd really rather avoid.