A disk I/O error is a general, unspecified problem with Zotero's ability to access your disk. If you have your Zotero data directory on a network drive or external disk, you should move it back to the local disk to avoid these kinds of problems.

If you're getting this error with your data directory on your local disk, there may be a genuine problem with your filesystem or physical disk, or security software on your system may be interfering with Zotero's ability to access the database.