I am having the exact same problem. I think I am glad that it's just not me.
When did you notice yours?
I noticed 9 to 5 Mac has a send a Tip link, Mac rumors needs one too.
I can see the head lines:
Mac app store hacked, 2 billions credit cards and passwords stolen
I'm not seeing that error here on 10.9.3. Must be a regional thing?
I'm not seeing that error here on 10.9.3. Must be a regional thing?
I'm in U.S.A. and not a part of the developer seed program and I still get the error, for what its worth.
--Edit--
I just switched from standard DNS servers for my ISP to Google's DNS servers and the error went away.
The problem is that someone at Apple has allowed the security certificate for swscan.apple.com (the Apple update server) to expire.
It's not something easily fixed on the user side.
Image
But how it can be expired for some users only....