Unable to download and upgrade v10.6.1 to v10.6.3.

Hello.

I was doing a software update in an outdated Mac OS X 10.7.3 to get all the latest updates through its Apple Software Update. However, one of them failed to upgrade: iTunes v10.6.1 to v10.6.3. After rebooting to let Mac OS X 10.7.3 to 10.7.4, Apple Software Updater shows it 97% partially downloaded. I have over 31 GB free, so it can't be a free disk space problem. I tell it to resume download, but it quickly fails from 169 MB to about 172.7 MB (176.9 MB is the whole size) with "The update "iTunes" can't be installed. The update could not be verified. It may have been corrupted during the downloading. The update will be downloaded and checked again the next time that Software Update runs."

I think the download is bad and is needs to be manually(?) deleted for me to retry. Where is this corrupted file at? Thank you in advance. 🙂