@slobrewer I unfortunately cannot debug the problem because when I attempt to set station values on my OSPi setup I get an error (most likely because I disabled all GPIO code). The, unable to communicate, error is because the file_get_contents is returning false which subsequently sends a 0 ajax return. That 0 tells the javascript to show the error message your seeing. From my limited understanding of the OSPi interval program I see it should support http://os_ip/sn1=1 so not sure what might be causing the error. The best thing you can do is navigate to the following URL on your browser and tell me the reply the OpenSprinkler Pi gives you.
http://IP_ADDR/sn1=1
That should turn on station one assuming the OSPi is in manual mode which is triggered by:
http://IP_ADDR/cv?pw=PASSWORD&mm=1
Replace IP_ADDR and PASSWORD with your OpenSprinkler configuration. If either are giving an error then that would be the problem we are experiencing.
Edit: Ray just posted that Dan updated the code for the interval program. Please try the new copy and let me know if the issues have been resolved.