It's just speculation, but I think this is what really happen... it 's most plausible IMO, but then it's pretty bad too cause we will have troubles to get an FW update / fix.
Found on yahoo answers:
It is not a network issue. The error is from a bad code written into the date program for leap year (February 28th). It is a firmware error that will need to be updated. This error only effects older version PS3s (Fats, not the slim version). This error is caused even if your system is not connected to the internet. Hopefully sony will release an update soon.
Leap Year isn't for another two years... but after reading this thread I went and turned on my launch 3yr PS3 and right away I noticed something wasn't right as the default theme color had changed back to December's Gray & White background when it should be showing February's Green background.
That's when I also noticed the date and time were no longer correct. Instead of
2/28/2010 9:40 PM it is saying it is
12/31/1999 5:38 PM, so clearly something regarding the date and time is not right.
However, I went to the Date and Time settings menu and while it would not let me set it automatically via the internet, I was able to change it manually.
That said, when I tried to log into the PSN, I am getting the
800105F error code.
I checked the PS3 web browser, and it works fine, so I knew the Internet connection wasn't the issue.
I then tried signing in on my other regional PSN accounts, like JP, HK, and UK, and none of them would allow me to sign in to the PSN, all resulting in the same pop-up error message as before.
The next logical step was to change the date to a past date, but that made no difference, and I was still getting the same error message.
It may be a coincidence, but it is interesting that on the same date this happened, SCEA made a huge change to their website and official forums.
I also did a search on Sony's official PSN forum for that error message, and until today there was no report of that error message before.
List of PS3 error CODES