This was down to adding a new column in the Links table which couldn't be filled with data. I'd set it to be Notnull but this caused the information not to be able to be updated in this column. This then had a knock on effect that caused the expiration date column to display a very similar date that you see (mine was getting stuck at a default of around 1970!!).
It was discovered by looking at the Apache and Mysql error logs.
Might also be worth asking dearnet;