Cool application, at least I hope. I have an 8830 and I just tried to send a GPX file with 500 (2.88M of data) caches to it. It actually sent pretty fast (about 30 seconds), but I have been on this step for quite a while:
7. Once the transfer is complete and CacheBerry displays "Analyzing GPX file" you can disconnect the USB cable.
I bet it has been Analyzing for about 10 minutes. FYI - It actually says, "Analysing GPX." You might want to correct that typo in an update.