Please send us a copy of your file at email@example.com and include a link to this thread. If it's too big for e-mail (>20 mb) you could use a service like SendThisFile, Adobe SendNow or WeTransfer.
I don't have good news. This file is corrupt at a low level within the underlying SQLite database Muse uses. I don't have a way to repair this file. I'm very sorry.
It would be helpful to know more about your environment in order to identify a pattern if/when we see this with other files. To date the other reports of this error during open have primarily been caused by files that showed clear signs of having been truncated due to incomplete file transfers or having been saved to removable media that was subsequently removed without being ejected. Your file doesn't show this type of damage. Rather it's the correct size, but contains blocks with incorrect data. While that could be caused by media failure, it seems more likely to be a bug somewhere in Muse.
Are you working on Mac or Windows? What OS version?
Was there anything unusual the last time the site was saved? Was the last save a Save or Save As?
Was the file saved on the boot drive, an external drive, a network drive, removable media, other?
Was the file saved in a DropBox folder? (If so, DropBox keeps a backup of previous saved versions.)
I did do an HTML export of the file – is there a way to bring it back from that?
I do save this on a thumb-drive but I had just saved it and then re-opened it later. This has happened a couple times to me and it’s really a pain. I really don’t want to have to go re-build this again. I can’t even open it in another web-program because of all the special stuff MUSE puts in it - it comes out all messed up.
To answer some of your other questions – see below the questions.
Any help I could get would be appreciated.
It's unclear from your comments whether you were opening and working on the .muse file while it was on a thumb drive or you just did a Save As to a thumb drive at some point?
I'd definitely recommend against working directly on files stored on thumbdrives when in any program. Removing a thumbdrive without first ejecting in the OS or having it temporarily jarred loose can result in truncated or otherwise corrupt files. It's much safer and provides better performance in whatever program you're working in to copy files to your hard drive and work on them there then copy them back to the thumbdrive when you're done.
The answers to my questions in your reply failed to come through in the support forum. The forum software is not as good as it might be at handling e-mail replies. If you could send the answers to me directly at firstname.lastname@example.org or use the in-browser reply feature in the forum that should ensure your response makes it to me intact. Thanks.