I just purchased a Sena MHS10-11.  After charging the unit I attempted to download the new firmware - the unit locked up and wouldn't power on without being connected to a USB source.  Here's what you'll need to do;

1) While plugged into the USB, reset the factor button using a paperclip - you'll need to keep it pressed down for 10 seconds.  It might take a minutes before you get a blue light on the unit.  Once you have the blue light, keep it plugged into a powered USB.

2) Remove the Sena Bluetooth device manager from you PC - including all files.    

3) Reload new software and create a different file name.

4) Start the recognition program, the software should recognize the unit and sequence through updates - when promoted by a message, hit the bluetooth switch and completed the download.

5) Once you get 100%, you might see an error message that notes the unit was not recognized - disregard and unplug the deive from the USB - you should have a BLUE, bluetooth light, with new firmware installed.

Note; the Sena technical service phone number is completely useless - the tech's speak english, but don't understand - its obvious the calls are being run through some remote center in a foreign country.  

Terrible firmware, terrible technical service - I hope I will be pleased with the performance...  Not impressed with how widespread this issue is and it hasn't been fixed...