My Xmarks bookmark synching service stopped working. I got a whole bunch of different error messages, most of which made it sound like it was either my fault, or the fault of a gateway between me and Xmarks.
But in fact, it seems to be a server problem at Xmarks:
Xmarks experienced a server problem on June 30, 2012. We are working to fix the problem now, we appreciate your patience.
Sounds bad. I can cope for now … but I wish the error messages in my browser had been more accurate and informative. And that they’d put a notice about the problem on their main homepage.