I carry Endnote files on a USB memory stick, and use the libraries on multiple computers, e.g. home and work. So I round trip the files, and I also sync them onto multiple computers. (Allway sync works great! Unlike that terribly ridig and error-prone Microsoft Briefcase product.).
Several times Endnote has reported corrupt libraries, and refused to open the enl files. The software suggests using Tools\Recover Library. However, I have found that utility does not always work.
Nonetheless, I have found a work-around that seems to work better than the recover utility: simply delete the whole associated .data folder, (not .enl file!), and then reopen the .enl file. It seems to work every time, and Endnote recreates a fresh .data folder. This seems to recover corrupt files that Endnote itself cannot recover.
The Endnote help file states that the .data folder contains other data: ‘This folder is considered part of the library; it includes figures, groups, and other files necessary for the library.’ In my case I don’t use that feature of Endnote, so the loss of the folder is of no consequence.
Anyway, I offer this workaround in case other users have problems with corrupt Endnote files and need a solution beyond the recover utility.
(Which raises the question: why is the .data folder so much more prone to corruption than the .enl file itself, and can the software developers perhaps fix that weak spot?)