As transaction occur, blocks are generated for those transactions. These blocks are basically layered on top of each other, and to know about all transactions, you need to have the entire block history.
So what it means or what you're client is telling you is the last block in its history is over 11 days old, generally this should read in the minutes range. Normally the client will catch itself up just by leaving the client open for awhile (progress bar at the bottom). If you're leaving it open and nothing is occurring, check that you're not blocking IRC connections.
Hi thanks
It's now saying last block was generated 21 secs ago.
It didn't seem to show the progress bar and sync either today, although it no longer says out of sync.
Please could you tell me how to go about checking I'm not not blocking IRC connections.
Thanks