DM pointed it out in our forums
not so long ago, but it's proven a rather large, worldwide, issue, with Sony even throwing out on Twitter
that "we're aware that many of you are having problems connecting to PSN, and yes, we're looking into it. Stay tuned for updates."
Theories range from hackers to Y2Feb, to just broken code. Whatever the cause though, avoid switching on your PS3 in the interim until the situation is fixed, if only to avoid any length update downloads should your data be corrupted. Sony are promising the situation will be addressed as quickly as possible and we'll let you know as soon as they let us know.