DB Cache not being read

[eluser]alex-uk[/eluser]
Hello, I've got a bit of a strange one...

I'm using CI 2.1 for a project and have run in to a strange problem with database caching.

I can run a query with caching turned on and the cache file gets written to the cache directory as expected. However, when the query is repeated the cache file does not get read! I can alter an entry in the DB and it is returned, or I can adjust a value in the cache file and it isn't returned.

I can delete the cache files and they get created again the next time the query is run, but still no luck getting them read!

I've been using CI for years and like to think I know what I'm doing (but maybe not)! Database is PostgreSQL if that affects anything.

Anyone any ideas?