I see this error occasionally when the attribute table I am trying to open has another table joined to it.
I am usually able to fix this by removing the join and creating it again. If that doesn't work, I've also had luck closing the project and opening it again.
Export the data to a shapefile first - does the exported data say anything like "empty output"? If so, then the data is corrupted. If it does not say this, then reimport it back into your geodatabase. Any error message?