It sounds like the output value simply isn't being received by the browser.
One thing you might want to try is to put this at the top of your app, and then check what shows up in your logs:
options(shiny.trace = TRUE)
It will record all the messages sent between the R process and the browser.
If you do it from the R console in an interactive session, you can see what the messages should look like. For example:
> runExample('01_hello', display.mode = "normal")
Listening on http://127.0.0.1:4044
SEND {"config":{"workerId":"","sessionId":"bbfb8c9d6a57acb188197f5f9e296fa9","user":null}}
RECV {"method":"init","data":{"bins":30,".clientdata_output_distPlot_width":577,".clientdata_output_distPlot_height":400,".clientdata_output_distPlot_hidden":false,".clientdata_pixelratio":2,".clientdata_url_protocol":"http:",".clientdata_url_hostname":"127.0.0.1",".clientdata_url_port":"4044",".clientdata_url_pathname":"/",".clientdata_url_search":"",".clientdata_url_hash_initial":"",".clientdata_url_hash":"",".clientdata_singletons":"",".clientdata_allowDataUriScheme":true}}
SEND {"busy":"busy"}
SEND {"recalculating":{"name":"distPlot","status":"recalculating"}}
SEND {"recalculating":{"name":"distPlot","status":"recalculated"}}
SEND {"busy":"idle"}
SEND {"errors":[],"values":{"distPlot":{"src":"data:image/png;[base64 data]","width":577,"height":400,"coordmap":{"panels":[{"domain":{"left":40.88,"right":98.12,"bottom":-1.08,"top":28.08},"range":{"left":118.08,"right":1093.52,"bottom":652.12,"top":117.08},"log":{"x":null,"y":null},"mapping":{}}],"dims":{"width":1154,"height":800}}}},"inputMessages":[]}
You can also use your browser's network logging to see the messages that are sent. For example, in Chrome, here's what it looks like when I load the app:
If you click on the xhr_send, you can see the information sent from the browser to the R process. For example:
And if you have the data:image/png... and click on it, then click on Preview tab, you'll see the image:
Hopefully this will help diagnose the problem.