To further add to this weirdness -

Sometimes when I try to edit a file, it won't let me save it as a different file name.

An example would be if I have a subroutine and want to make a slightly different version of it.

The "save as" option is grayed out. So the only way to save a different version is
to close the VS environment, then reopen it.

This problem seems to have occurred in recent versions. A bug introduced by changes they made.

Why would they disable the "save as" version, anyway?

I was wondering about that -
but some files CAN be saved with "save as" even while debugging.
So I have no reason to think that the feature is completely disabled.
I played with it - and "s'top debugging" does not change anything.

To add further to the drama; it told me a file was present in the
solution set, even when the file is not listed there.

So I think it's somehow losing track of which files are present or otherwise.
That's why it discards files that it thins are gone, and they are lost.

But as I said earlier, a simple fix would be to make a backup of any file that
is being edited, rather than discarding it until it is stored.

Hi Ian; Maybe in my case the automatic save is not enabled. So, where do I turn that on, just to make sure? Unfortunately, screen shots won't show the problem, since I can't screen shot something that disappeared. I don't get ANY warning or error messages, it just happens. In other words, I go back to the original file I was editing, and it's nowhere to be found. If it's deleted, why isn't it in the TRASH bin? It might be helpful to find out exactly what VS 2010 does with a file when you open it for editing. Have you ever exprienced a source file disppearing from the Solution Space list, aside from whether it was recoverable? Generally the ones that disappear are those that I was editing, but are NOT in current focus, i.e. the tab is on another item. If you'll pardon my "soap box," I still think making a .BAK from .F90 when open for editing would be a simple fix.

I was wondering if this could be caused by anti-virus software.
But usually this would manifest itself by being unable to attach a file,
if the AV software has grabbed it first. Sometimes I do experience a problem
doing a build which I think is caused by the AV package.

So, what does the VS package actually DO with a file when it is being moved into memory for
editing? If it's in "limbo" then having it just in memory is an open invitation to lose it
permanenly, perhaps? As I said earlier, just about every editing package I have ever seen
makes a temporary backup of any files moved into memory, to forestall a problem like that.

The problem seems to be aggravated by opening another tab while some other file is open for editing. I assume then, that any files open for editing are just residing in memory, not on the hard drive.

Anyway, if you know where I can get a file versioning system like you mentioned, I will take a hard look at it.

Another possibility would be a BATCH file that runs every hour or so to make copies of F90 files in the background.

I do back up everything on a continuous regular basis, using MyBook, but
even though it does it continuously, the file disappears before MyBook can access it.

I do also use a CTL-shift-S to save everything, but apparently not often enough.

If the file is "left untouched," why would it disappear?

If there was a SURE way to make it happen, I would describe that.
You don't use remorte assist, so there is no way to have anyone look at my system
environment to see what's going on.

That was one of the first thing I considered, but I
don't understand why I would only see this during
the usage of VS 2010.

Otherwise, I would see it it other usage environments.

Why would a source file vanish from the Solution space
anyway? Even if I can recover it, it seems rather weird.