A managed solution cannot overwrite a Attribute component on the target system that has an unmanged base instane.
Error Detail Message
A managed solution cannot overwrite a Attribute component on the target system that has an unmanged base instance. The most likely scenario for this error is that an unmanaged solution has installed a new unmanaged solution has installed a new unmanaged Attribute component on the target system, and now a managed solution from the same publisher is trying to install that same Attribute component as managed. This will cause an invalid layering of solutions on the target system and is not allowed.
The error caused by....
There is one publisher that named "Company one publisher" and this publisher have imported the 1st unmanaged solution that included User Entity.
Ok, now this publisher try to import the new managed solution that included again User Entity. but this time, the above error message will show in import log.
So, this error will appear when same publisher import different type (managed, unmanaged) solution that included the same entity.
How to solve....
Finally, we import again the 1st unmanged solution as managed solution. So both solution are managed solution. So, don't do the different type of solution for same entity for same publisher.
Label: MSCRM 2011