I do not remember the status bar only being half way when the prompt came up. I have used the appropriate reader on EV's and V7 varieties and I'm pretty sure the status bar was at the end or very very near, NOT half way.
I would not load another map until this is sorted. Per the size you "should" be fine but I would wait.
Do you have another computer to try with?
Also there is a long Guzzidiag tutorial thread on here that may some some info for you.
WITH my WAIT in mind.......... You "could" try loading the map you just downloaded back in and see if it loads correctly. BUT IT COULD "MAYBE"!! BRICK THE ECU?????? IF IT FAILS.
I would wait and hear from Beetle first to be safe!! And if you do try, don't blame me 
Tom
I'm not going to try and load any other Map until I get a perfect read on my old one. Not worth having down time on the bike if something goes wrong.
I've read through the thread a few times, and have been trying to trouble shoot this a bit myself.
I've tried
Different USB ports
Different Lap top
Having the battery hooked up to a tender
Uninstall and reinstall of the reader app
Firing up the bike for a bit, turning it off and trying again
Checking the ECU version on Guzzidiag
at this point, I'm actually thinking it may be a hardware issue with the connector, and I've sent a note off to LonElec to see what they think. I shot a note over to Beetle as well to see if he had any thoughts.
Ill update when I figure it out.