Aperture works more reliable with locally mounted volumes. Copy the library from the MBP to an external drive or try again by connecting the machines directly in target disk mode, if you have a firewire cable or thunderbolt cable: See this document: Transfer files between two computers using target disk mode
Also Make sure, that all libraries are in good repair. Run the Aperture Library First Aid Tools on both libraries, to ensure that their are no permission problems and the database files are consistent:
See: Aperture 3 User Manual: Repairing and Rebuilding Your Aperture Library
The merge sometimes does fail, if Aperture assumes the libraries you want to merge to be duplicates of each other. Two things to try:
- When you are prompted if you want to merge or to add, try "add". This way you will import duplicates, but at least you will import your library.
- Or turn the MBP library that you want to merge into your iMac library into a new library first: import it into a new empty library, then import this new library into the library on your iMac.
Regards
Léonie