As a replacement, I'm using Sliding Read More, which works perfectly (and with a nice visual effect). The following is only useful if you're running an older version of WordPress.
Recently (and very smoothly), I moved a couple of sites, including robservatory.com, to a new hosting company. I had been hosting with my good friend James, who runs Find Mac Stuff, for many years, but my small sites were really on too big (ie too expensive) of a server for my simple needs.
The move to the new company went well, with the exception of my favorite plug-in here, Ajaxified Expand Now, which expands articles in place, saving a page reload. It was returning an error message ("Error while connecting to the server. Please try again later.") instead of the content. So I disabled the plug-in, but asked James to take a look at the code.
After some trial and error, he came back with a simple fix--it turns out that a line in the code was specifying an incorrect file and an incorrect path. For whatever reason, despite the mistake, the code worked fine on James' servers, but not at all on the new servers. The simple fix is this...around line 62 of the plug-in (version 0.8 beta), find and change this code...
...into this code...
This fixed the problem completely, and the plug-in is now active on the site again, as you can see by reading this very post! So if anyone ekse is running this plug-in, and is experiencing the server connection error message, try this simple fix--and thanks James, for finding the error (and for the great hosting all these years).