After ABR 10 to 11.5 Upgrade, ABR keeps reporting license errors

Hi,

After upgrading Acronis Backup & Recovery 10 to 11.5 we keep getting the log alerts:

"The license of the previous product version has been specified".
Event code: 0x00CA0019
Additional Info:
Error code: 25
Module 202

However, the upgrade licenses have been successfully added during the installation.
Even a full uninstall and reinstall of 11.5 with the correct licenses (Base 10 + 11.5 upgrade license) the same error messages appear.

There is a similar request in german here: http://forum.acronis.com/forum/45544
However, even after uninstalling ABR 11.5, then deleting the whole HKEY_LOCAL_MACHINE\SOFTWARE\Acronis branch and reinstalling, the problem persists.

OS is Windows Server 2008 R2.
Of course the Acronis KB doesn't help in any way.

What may be the root of the problem?

Thanks.