Got this error while updating from 2.5 last beta to 2.5.0 release.
[Blocked Image: https://dl.dropboxusercontent.com/u/46231099/IMG_0029.JPG]
On retrying while it detects the pen drive, it won't detect the update even after I've formatted and re-downloaded and the new 2.5.0 release on to the pen drive.
Had no issues updating previous releases.
edit:
I gave it another shot after a break, it detected and worked!
All cool here 