There are many reports within the Teegle SL horse community of rezzed horses being unable to communicate with an external server which are thought to be due to some issue pertaining to SL servers. I do not know whether or not this is so (this simulator-server part) but this looks very much like the http out communication issue that precipitated the roll back of an RC channel update recently. Perhaps we will find out soon?
Looking back, similar issues were observed following the RC channel roll on 23rd June. The problem server software was 560618, which was replaced by 560819 which is now running Grid wide and since the version has been on the RC channel for over a week now, it seems unlikely to me to be an issue emenating from the Server software.