Make sure you have the latest version of K-manager, as the older ones tended to corrupt the downloads often.
Once connected with ignition on, choose online -> tools -> download.
As soon as its downloaded, do file -> save as, and call it something.
Quit out of k-manager. Re-open k-manager, and file -> open the calibration you just saved. then have a look through the tables and parameters, and check the tick over etc don't have stupid values in, or tables have lots o zero's (sign of corruption).
Once you have a good copy, just open that, make any changes then upload that. I stupidly once did not check a downloaded map, made changes and uploaded it. Come Monday morning, time for work - car won't start due to corrupted map. Luckily I had a decent copy to re-upload.
I think these problems are alot better now with newer k-manager.
Jon