Sony has scheduled a maintenance of the PlayStation Network starting on the 25th of August. This will be affecting all PAL regions of the network.
The maintenance will commence for a scheduled time of just over seven hours. (You can find out the exact time for your region here). The affected services during the outage will be the PlayStation Store, PSN Account Management, PSN Account Registration, Entertainment Services, Online Gameplay, and the ability to log into PlayStation.com websites under the PAL umbrella of regions.
There is no word at the moment if the North American PlayStation Network will be affected by this maintenance.