Q: How can i download purchases when 'this computer is already associated with an apple iD'

This has happened many times when using iTunes.

My iTunes is authorised with this computer, and i can make purchases off the iMac I'm using and

have the music be in my iTunes library.

BUT, I also have an iPad, and I've downloaded a few songs off iTunes on my iPad, and I'm having trouble

re-downloading them to my Mac.

I went into my user>purchases>download all

but it came up with a notice saying:

'This computer is already associated with an apple ID,

You can download past purchases on this computer with just one Apple ID every 90 days.

You cannot associate this computer with a different Apple ID for 64 days.'

Please help? Ive seen this notice before, and I think i just hit 'Okay' but I can't download my songs to my mac now.

Thanks a lot xx

-Olivia M