When upgrading from BES 5.0 SP4 MR5
BES 5.0 SP4 MR8 I got the error message
"the upgrade cannot be installed because a previous version of the installation has not been completed"
No logfile was written at all.
upgrade from MR5 to MR6 worked, but stil i got the error message when trying to upgrade from MR6 to MR8.
Fortunately I was pointed to
KB35907-Unable to upgrade to BlackBerry Enterprise Server 5.0 SP4 MR7
the scenario is the same, only the errormessage changed.
for me changing the mentioned registry entry from 1 to 0 worked.
Well I'm not the most famous google specialist so due to the changed error message it took me a day.
A short hint in the known issues section of MR8 release notes would have been great