MMC cannot open the file XXX.msc

A copule of weeks ago, my home machine started to show a weird behavior. Suddenly, both Diskeeper nor the normal windows defrag.msc didn´t work.

The message was something like:

"mmc cannot open the file XXX.MSC. This may be because the file does not exist,is not an MMC console, or was created by a later version of MMC. This may also because you do not have sufficient access rights to the file "

Right, after googling it I´ve found several solutions. Ones say that this fixed their problem (enabling offline files). Others (like me) fixed it running:

regsvr32 "C:\windows\system32\msxml3.dll"

This will re-register msxml3.dll. If successful, a dialog will come up saying that, and now your msc files should work again.

I don´t have a clue about what caused this problem. Anyone knows?

Thanks!