Kazaa .dat files get deleted!

I have Kazaa and recently the computer has been low on disk space, so I copied the .dat (temporary downloaded) file onto another computer in the network. Then, because the computer ran out of space it said ‘Failed’ in Kazaa. So I cleaned up space, and copied the .dat file back into the directory where it originally was. But when I restart Kazaa, it deletes it! It was a 550MB+ file and had about 50MB to go…
I have the .dat file…how can I get the download working again?