I get the same problem with a shipping build.
I have just upgraded to the git 4.6, and I am currently still having issues. Attached is the error, but here is the html5 build itself on our website http://dev.sandboxr.com/html5/SbxApp.html
Using Firefox 32-bit…
After correcting the naming issue in the HTML file by changing jStorage.js reference to jstorage.js (the actual filename). The app compiled and loaded into this runtime error in the attached file.Unreal web app console output
Here is the log from the Firefox Developer Web Console…
So - I am not entirely sure why this is happening without seeing the source code and I cannot reproduce this with my test case - however the best I can see is that perhaps the Verb is not set from the error messages - Is a call to SetVerb is missing?