So if you type in "admin" as the account name and leave the password box empty, you can't get the file to open?
Have you checked File Options?
If you download a copy to your local machine can you once again open it as before?
Strange. I don't know what happened, but I closed, then downloaded the file off the server. Opened from my desktop. (BTW, just to get it to work so others could see it yesterday, I gave the Admin account a password). Opened using the password I gave it yesterday successfully. Then went to Manage>Security>Accounts....cleared the password so that it is blank, saved and exited.
Verified that the file could then be closed and re-opened on my local machine using the Admin Full-Access account successfully.
Shared it back to the server in this configuration. Bingo, now it works.
I suppose it needed some attention of some kind. This file was doing all sorts of weird things yesterday too. I have some scripts running, and was in the process of testing some of them. I had it working like I wanted before uploading to the server. But at that point, I never even went into the Manage>Security section at all, so at the point that I asked the question yesterday, that part of the file hadn't been changed from the time it was created.
Works now. Back to the development drawing board.
Please note that a change in File Options--this is not in Manage | security, can alter this behavior.
This file was doing all sorts of weird things yesterday too.
That's really vague but perhaps your file is damaged. Run a recover on a recent copy and see if any issues are reported by the recover.