I have a Drupal 7 site that runs on Windows 7 and SQLServer.
Recently, when users try to upload pictures or files they get an error message:
File could not be saved. An unknown error has occurred. The file was unable to be uploaded.
I have a development and a test site. The site was on Drupal 7.20, then upgraded to 7.23 and it worked for the development and the test sites. However, it did not work in production.
In production I upgraded to 7.23 and verified the elfinder is using library files 1.2.
I am not sure why this is happening: No code was changed before the Drupal core update, and the error is sporadic.