Hello to everyone I am new member and I thought this guide would be a help to others like the OP and myself who had trouble updating the Star Adventurer.
I was able to update my Skywatcher Adventurer was as follows:
1..Download & unpack the 'Prolific USB-to-Serial Device Driver'
2..Download & unpack the 'Motor Controller Firmware Loader, Version 1.74' or greater
3..Download & unpack the firmware 'Star Adventurer Mount, Version 3.06' or greater
4..Install the 'Prolific USB-to-Serial Device Driver'
5..Connect the Star Adventurer via the mini USB
6..Run the Motor Controller Firmware Loader
7..Turn the dial to the 'Star symbol'
8..Browse to were you unpacked the MCF firmware file and click update
9..Once the firmware has finished updating turn the dial to 'off'
10..You should now have a successfully updated 'Star Adventurer Mount'
I hope this little guide will be of help to you and other who is having the same problem.