Sign in while you can.
Last night on their official forums, Sony announced that there would be scheduled maintenance on the Playstation Network today, starting at 12:00 EST and ending at 19:00 EST.
There’s still time to sign in to the PSN before the maintenance begins, which Sony recommends doing to avoid problems during the actual maintenance. You can read the official statement below and follow Playstation on twitter for updates.
“In order to continue bringing you the best online games experience, we will need to perform some routine maintenance on PSN beginning tomorrow morning (Thursday, August 23rd). This maintenance will start at approximately 9:00AM PDT (10:00AM MDT / 11:00AM CDT / 12:00 noon EDT) and last until around 4:00PM PDT (5:00PM MDT / 6:00PM CDT / 7:00PM EDT). Specifically during the first hour of this maintenance period, you may receive a maintenance notification when attempting to access PSN. The PlayStation Store and Account Management will not be available during the maintenance period but you WILL be able to access online play and apps provided that you have signed in to the Network at some point over the past few days. So please be sure to sign in now if you wish to access the Network during this maintenance window.”
[Source: Playstation Forums]