Cannot open bib file

After using Jabref 2.9.2 for past several years on Mac OSX 10.7, I migrated to
Mac OSX 10.11 and Jabref 3.6. I am not sure, how it happened, but I cannot
open neither database or its backup. In both cases, the error message is
Error in line 4: Expected { or ( but received 0. I wonder, whether this issue
that can be fixed, somehow. I still have a one day old backup of this database,
so I am on safe side, but I will miss a few entries. Thanks.

Could you please upload your bib-file here or send it to so that we can assist you better in fixing your problem. Thanks.

I opened the “corrupted” bib file in the TexShop. I think, the issue was with invisible character
preceding %. After I removed this character manually in many, many instances, I was able to open
this modified file in the Jabref.

“Invisible characters” and the like are a typical indicator for encoding issues. Please make sure that your applications (TexShop, JabRef, etc.) are configured to actually use the same encoding and, more important, that they use the encoding in which the file is actually written.

I really don’t know what is going on. I imported one or two citations and I
saved and quit Jabref 3.6.
When I try to open it, I get the error message Error in line 4: Expected {
or ( but received 0.
The database is in the attachment. Thanks​

I just downloaded your file and opened it with the current development version of JabRef (which is only a tip ahead of the standard 3.6 version). It opens perfectly well on my machine, is searchable, I can add entries, save the file, reopen it, etc. etc.

Sorry, but I cannot help you with this one. From my side, the problem seems to be localized to your system.

Same here: I could open / modify / reopen your file without problems on JabRef 3.5 Windows 10. Did you tried open the file on a different system?