Every time I try to update iTunes, my computer tells me it has an invalid signature and removes the download. What can I do?

similar problem - upgrading iOS on my iPad through iTunes required a prior upgrade of iTunes to 10.6 - during that process the message "iTunes has an invalid signature" appeared with advice to just download iTunes and install it manually afterwards. The 74MB download repeated, but ended with the message "iTunes has an invalid signature. The download has been removed" - no more options so I called Apple Care today 13 March. It's a timed call to a 1300 number. After taking details, the operator, Gabby, said she "thought" the solution lay in bypassing iTunes on my PC and doing the update over wi-fi. She directed me to the Settings app, but it appeared that her thinking was in error as there was no update option there. She then said she'd have to put me on hold to go and talk to someone. She said she could not call me back. I expressed my dissatisfaction and asked to speak to her supervisor. She put me on hold and 6 minutes later I hung up. This is the level of "Apple Care protection", a paid "service" for which one pays telephony charges while the staff research a solution. I've also found lots of other references to this invalid signature problem, but so far no solutions - Apple knows our email addresses, but doesn't publish a solution ...

Apple, where are you?

Actually it didn't take too long to find the solution to that problem by searching on Google: just download the latest iTunes directly from the apple websiteusing your browser - don't do it through the installed iTunes program. Once downloaded, just run the file and it installs the later version over the top of the old version. All that happens without (for me) any hitch. Note - the solution obtained from one of myriad sites complaining about this problem; solution NOT PROVIDED BY APPLE.