I have a similar problem. The only thing that is mentionned is unexpected reasons
Are you receiving some type of error/message that tells you this?
When are you seeing this?
The software that I am trying to install are updates to system 10.7.4 to obtain 10.7.5.
So you are not trying to update iTunes (this forum)?
I recommend you post over here -> https://discussions.apple.com/community/mac_os/mac_os_x_v10.7_lion
with a bit more info.
When specifically do you get this message?
Is this a message that pops up?
Are any other porgrams running?
Have you ran software update, etc.?