Quote Originally Posted by sinn3r
The problem could be related to a recent update of whatever anti virous your're using.. try disabling your anti virous and see if it works.. if it doesn't.. start windows in safe mode.. and try to open the file.. see if it works fine.. if it does.. the problem is most probably caused by a program that is running in the background..
I thought it would be something like that too so i put back some backups i had but the problem remained.
But then I realized "I COULD be I have not been running Excel on this PC for ages and my backups could ALSO be 'invalid' regarding this behaviour" so finally I decided to reinstall everything (including all other software it costed me almost a weekend !) and indeed Excel does work again.
So obviously the problem has been around at my PC for over half a year (at least) and I can only look at it like "cause unknown but solved".
Now i DO have a backup that IS functional regarding Excel (and the rest I hope [I have several intermediate backups now as well and I reinstalled the 'final backup']).

But what comes into mind is that it SHOULD be possible to repair Excel (Office) in such a way that it WILL work regardless of what has been at the PC or at least it should clearly identify what is preventing it from working well (what files, registry settings etc) in order to have a look to solve the cause of the problem rather then just requiring a total reinstall of the system.
Especially as Office is know to be THE moneymaker at MS extended information about problems with it (best : including a "for sure" get it running repair facility) seems someting missing.