I was visiting a customer last week who kept seeing an error message declaring that a 'field ABCXYZ' is inaccessible.
The strange thing was that this field was not actually on the page layout, or visible in the field editor within the Object editor.
This blog talks through how I tracked down and fixed this issue.
Fields in Packages
To track down this mystery field, I copied its ID into the last part of the Salesforce URL
Once I pressed return on this, I could see that the field causing the error was inside an package that had recently expired in the ORG.
This was slightly strange, as the user who was experiencing the error wasn't a licensed user of this package, and had never used it before. The error had not occurred until the package itself had expired.
Removing the expired package solved this user's issue.
I found it intriguing that the fields and workflows within the package were still being referenced and/or running in the background even when:
a) the current running user was not a licensed user of the package
b) the package itself had no current active licences
So, if you ever come across this error in future you may want to check for an expired package in your ORG as a first line of debugging.