Like I posted in another topic:
"Hi everyone,
Like multiple users posted already, there seems to be a fix to the errors.
I got WP 8.1 with Cyan as a developer preview user, just before Microsoft halted the update because of the Bitlocker problem. Using Nokia Software Recovery I have downgraded my Lumia 625 (CV, Dutch) to WP 8.0 with Lumia Black. After that I got a minor update making my phone ready for 8.1 and the next update was the official "non-DevPreview" OTA 8.1, which came with Cyan.
Then I installed the developer preview app again and got the 8.1.1 update, which cleanly installed without the aforementioned error.
So I can confirm that downgrading a L625 to 8.0 with Lumia Black helps in getting the latest update. For the people who don't want to reinstall everything again: make an update before you do this procedure. After you get the 8.1.1 you can do a hard reset and reinstall the backup.
Oh, another thing: the 1,39 gigabyte update was downloaded twice by the Software Recovery tool before it 'caught on'. Seems to be a known hickup with the tool.
Ciao,
Arie"