I had this happen one time on an older version of Mandrake Linux, it hasn't happened to me with any version of Mandriva, yet. I believe that what happens is Kget picks up the wrong file size off the server... I don't know why, nor can I prove this theory. To fix this I had to delete the ~/.kde/share/apps/kget/logs and remove everthing from the ~/.kde/share/apps/kget/transfers.kgt file except the first line
[Common]
This should fix Kget for you, but it will not save your 2GB d/l. I'm sorry, but I know of no way to resume and save that file for you with Kget.
For the record, I use wget for anything over 500MB, because I can resume anything that gets screwed up while d/l with my connection.