Same problem here. That same keynote downloaded about 10 times overnight (last week) but I didn't end up with 10 copies, only 1, they seemed to get deleted after being downloaded but used up a lot of bandwidth overnight.
Once I noticed that it was happening I stopped the downloading cycle/loop and then triggered the download again by clicking on the cloud button next to the podcast entry. Once downloaded I synced it to my iPhone and I thought everything was all good.
This morning I noticed that the podcast was no longer in iTunes on my computer but my iPhone still has it. I have not watched it so it didn't delete it because it had been watched. I re-downloaded it to my computer by clicking the cloud button.
Then I clicked the podcast refresh button (3 quarter circle with an arrow at the top, left of the podcasts window) and the podcast got deleted and started to re-download! I can't get this to stop happening, probably have to unsubscribe from the podcast.
My settings for this podcast are: Subscribed with keep "Last 5".
I would also note that this is not a new problem, I have had this before with this very podcast. Previous keynote podcasts have re-downloaded themselves multiple times but this time it seems to be happening more often for some reason.
iTunes 11.1.1 (11) on Mac OS X 10.8.5 but, as mentioned above, I have had this problem in the past with older versions of iTunes and Mac OS X.
