What should I do when "An error has occurred" when downloading Lion?

Solution 1:

I have sorted the issue. I just had to use a different router. The BT Business hub that I previously been using had a problem on it which prevented anything above 2GB do loose connection. This would explain other problems as well.

Solution 2:

I had a similar event. I was able to solve the problem by:

1. Signing out the app store
2. Closing app store
3. Clearing cookies in safari (evidently app store uses safari's cookies)
4. Reopen app store
5. Sign-in to the App Store
6. Press Option and click Purchases
7. Click Resume on OS X Mountain Lion under Other Purchases

Maybe this will help?

Solution 3:

Because a lot of Mac users are probably doing the same download now. It's probably overloaded. After all 4 GB is a good bit bigger than an iTunes song or an iOS app.