User Profile Service Application upgrade issues

Hello all,

I am doing an upgrade test from SP2010 to SP2013 following the technet article

http://technet.microsoft.com/en-us/library/cc263299(v=office.15).aspx

At some point, you need to export the encryption key and import it to the new farm.

The export operation goes just fine, but when I try to import it on SP2013 using the command

miiskmu.exe /i Path {0E19E162-827E-4077-82D4-E6ABD531636E}

I get the following error:

"The operation encountered an error and cannot be completed.
Error: Object reference no set to an instance of an object.
Error Code:80004003

Has anybody had this problem while upgrading the UPSA?

Thank you.