To be certain you avoid common problems like Sprint's cache, misconfigured MIME types, and corrupted JAD files, always try at least once to send your MIDlet using the Uploader tool here at SprintDevelopers. It's best to upload the JAR without the JAD and let the Uploader construct a proper JAD for you.

Sometimes your JAD will contain special attributes that are used by your application so you may need to upload a JAD for your MIDlet to work. However, if you are having problems just installing a new program, try it without the JAD. You might be able to quickly determine that you have a corrupted JAD file.