Comment 1 for bug 743020

Hm, odd. That error message probably means that software-centre's X connection has been closed - it's trying to write to a socket that no longer works.

That's not a common failure mode for X applications. I can't seem to reproduce it, but failing anything else, running software-centre under “xtrace” would print all the X protocol traffic that's occurring and the point at which it starts to fail.