Sony has announced planned PSN maintenance for this coming Tuesday, 31st May.
The service will be offline from 7pm that evening until 1am Wednesday morning, wrote Sony Community Team member "RabidWalker" on the European PS community forum.
During that time you won't be able to use:
PC Registration
Console Storefront
PS3 Account Management
PS3 Network Account Registration
PSP Network Account Registration
Qriocity Account Management
However, if you're already signed in you will stay connected. You won't be able to use the above services, though.
The post doesn't mention PlayStation Store. Will the PS3's virtual shop finally re-open on that day?