Some steps to attempt to resolve lockups when opening itunes.
I have the current model (2010) macbook air and since updating all the software including an itunes and osx combo update everything freezes and the only resolution is to power down and back on again.
Any attempt to open itunes freezes the computer completely, from reading up it seems this issue is isolated to the current model of the MacBook Air.
Following articles such as this one: http://discussions.apple.com/thread.jspa?threadID=2790878&start=30&tstart=0
I have found some different techniques to try and resolve the issue but these seem to be temporary fixes around permissions issues.
People have gone to the extreme of wiping their osx install and instaling all combo/incremental updates with an empty itunes library and still seeing the issue when patches are up to date so this issue looks to be in the release of the latest combo fix.
The list of fixes for different people are listed as everyone seems to have a different fix, I’ll try to keep this list up to date and in order of easiest to most complex.
1. reboot twice in a row without opening itunes - Simple as it seems, it has resolved the issue for some
2. run disk utility and choose “repair permissions”
3. An article at Macnn suggests the following: “A second method in case the first one doesn’t work involves locating and deleting the file “iTunes Library Genius.itdb,” which is located in a user’s home folder inside the iTunes folder, which is itself inside the Music folder (or ~/Music/iTunes). The user then launches iTunes but immediately quits it, and then launches again closing the sidebar. The action forces the Genius function to rebuild its database, which appears to resolve the issue.”
4. run disk utility and repair permissions in safe mode - some files are inaccessible when not in safe mode so this can circumvent that issue, safe mode is accessed by holding shift when powering on and booting the machine.
5. run disk permissions when booting from the osx install usb stick - again to get around issues with files that are being accessed by the running operating system this is just a more extensive and complete way of repairing the permissions
6. wireless internet related - some people seem to be seeing problems related to their wireless, I actually lose my wireless settings for my wireless networks after this lockup myself, the suggestion is to use an ethernet adaptor and try disabling wireless all together.
Hopefully one of these many fixes holds you over until apple decide to fix the issue.