OS X Contacts app error and unable to restore .abbu backup

I kept getting an error popping up in my Contacts.app saying:

“The operation could not be completed.”

“No other information is available about the problem.”

I figured I’d try to remove all my contacts and reimport them, so I exported an .abbu file of all of them and then deleted them all. I then turned off iCloud, before reimporting them, thinking if I turned it on again after doing so it’d re-sync them up to iCloud. What happened however was that it re-enabled the iCloud account straight after reimporting the .abbu file and then deleted all the local contacts straight away as it synced with my empty iCloud contacts. The solution was this:

• Firstly remove your network cable or turn off your wifi to disconnect from the internet.
• Import the .abbu file to restore all your contacts, which will no longer disappear again as it can’t connect to iCloud.
• Now select all your contacts (select one and then press cmd+A) and drag them out to your desktop, which will create one .vcf file with all your contacts in.
• Reconnect to the internet and your contacts should disappear again as it re-syncs with iCloud.
• Next, just drag the .vcf file from your desktop back into the Contacts.app and it will reimport them all and then sync them up to iCloud.
• All your contacts on your iPhone, iPad, and other Macs that are synced with iCloud should now have all your contacts back.

Hope that helps someone else.