I had similar issue with my OTA deployment.
You will have to make sure that:
1) correct mimetype set in http server (for .cod and .jad file)
2) set the .cod and .jad file in the correct location on the http server (which is obviously done properly, judging by the error code)
3) clear the browser cache !
Number three has caused me a headache
for two hours, because the Internet Browser did not re-query the server but used the already retrieved (and at the time it was first requested a faulty .jad/.cod file.
Hope I helped (somebody)