Suddenly and with no reason apparent to me about half my data files became inaccessible by 2018.3 a couple days ago so I upgraded to 2018.4. Same problem with the same files. Half open up normally. All data files - those that come up and those that don't - are stored in the same local directory.
I have attached a couple of screen shots of messages the system returns when I attempt to open the 'bad' files.
Any thoughts are appreciated. Some of this data is 20 years old. Not a disaster but would like to retain the history if possible.
Many thanks