Try a system restore first, often the simplest way to revert to a previous working state, if it works it may be worth holding off doing the update, at least until more becomes known, and hopefully if it's an iTunes issue they will release a more stable update in the near future, or an expansion of above, you can try Apples response to such an issue Here.
Should you wish to try and use various fixes to repair this, then there are a few threads on this in the Apple forums, the best way to approach IMO is by the least risk order, so the safe option is if you have not done so (assuming you have a system with Admin requirements), is to try installing again, this time right click on it, and select to install as Admin, some programs need Admin access to install or work properly, please note there may be some repetition of "fixes" due to varied attempts rehashed.
Next is there is a suggested uninstall, but they list it be in a specific order, I have no idea why this is (on the basis of what happens if done differently), but that's what is said, it states the order as being:-
iTunes
Apple Software Update
Apple Mobile Device Support
Bonjour
Apple Application Support (iTunes 9 or later)
Then reinstall via right clicking on the install file and selecting Run as Admin, fingers crossed this is the most you will need to do.
There is also a suggested repair that involves creating a .bat file to extract the Apple Application Support file, but there is a far safer way to do that, if you have file compression software try right clicking on the iTunes install file, then select extract here (it will extract the files to the same location), if you don't have such an option then get and install 7-Zip, and you will be able to do this, it will simply separate the install files so you can simply reinstall the Apple Application Support element which appears to be the weak spot in all this, hope something here helps.