Currently Being ModeratedJul 15, 2013 7:09 AM (in response to Bolthouse999)
You don't say which version of iTunes you're using. However, I found this advice on another forum, given to a guy who had also let his space get almost full up and who got the same error.
First, uninstall iTunes and the related components by following these instructions: http://support.apple.com/kb/ht1925
(Oops - I just noticed that was for Windows users - you will want to hunt down the Mac version of that Knowledge Base article)
Then there was some advice about using something called Ccleaner to clean and maintain the System and get rid of temporary files etc. I have removed this as I am not familiar with that - I use the free software Onyx, which will do a similar job. You may or may not want to do that part of it. Make sure you download the Mountain Lion version as Onyx changes with each new OS release.
Then he goes on to say :
Once this is complete, reinstall iTunes from the following link:
If you still have problems, then I would go through these steps again, and then try an older version of itunes, which you can upgrade after.
Rest assured, that uninstalling and reinstalling iTunes won't delete your music or videos or apps, which live inside your iTunes folder in your Music folder, and which you will not be touching.
Bear in mind, it is VERY bad practice to let your HDD fill up. OS X needs a minimum of 10-15% - preferably even more to avoid slowdowns - to use for cache and temporary files.