Long time back, I wrote a post on how to solve “Another blog is already hosted at this address.” problem when you are using custom domain for your blogspot blog. It included a few steps to follow. Though it’s not that tough, if you are too lazy and willing to wait sometime, you can delegate the work and sit back till your url is cleared of the problem
Just submit your Blogger blog url in this Google spreadsheets form. And they will clear the custom domain url from the problem. Only draw back is that it might take till 48 hours to fix the issue for them.
If you don’t want to wait that long, you can use the method mentioned in my previous blog post