post.php strangeness

Well. I am seeing some weirdness when posting to my blog.
For some time now, I have been getting this error immediately after submitting a post in Safari:

Safari can’t open the page “http://slumberland.org/wp/wp-admin/post.php�.
The error was: “bad server response� (NSURLErrorDomain:-1011)

This looked somewhat alarming, but it never interfered with actual posting — the posts always appeared on the blog just fine, so I never bothered to look into it further.
Well, I just made another post, about my problems sending pings to Ping-O-Matic, etc., and I started to wonder if the two problems were connected. It’s possible they began at the same time.
So I just tried to post in Mozilla, which I usually don’t use for my blog, to verify whether the error was limited to Safari or not. And guess what — I didn’t get the “bad server response” error in Mozilla — instead, it triple-posts. Every time. I click “publish” once, I get three posts.
So something is broken in my posting process here, but I don’t know what it could be. Does anyone have any ideas what is out of whack here? I’ve searched the forums but not turned up anything.