When downloading updates for Quicktime 7 and Itunes 10 I keep getting an error saying that files shared by these updates has an invalid signature and that the downloaded has been removed.

When downloading updated for Quicktime 7 and Itunes 10 I keep getting an error saying that files shared by these updates has an invalid signature and that the downloaded has been removed. If I don't get that message I get a message saying that the download was unsuccesful and that in order to download I need to go to tools and then select dowload only. Please help I really want to update my iphone!