I encountered this exact problem yesterday with iTunes and later discovered that CS3 was also affected. I didn't try Office X. FWIW, here's my solution:
*I deleted the copy of Curlz MT that was installed by Office (Office/Fonts). CS3 and iTunes now work again.*
How did I get there? You might well ask. I tried trashing the prefs, deleting and reinstalling iTunes, etc. And yes, iTunes would still open for other users on my iMac. I tried Disk Utility (via install DVD), repaired the disk, repaired permissions... still no love.
I was discussing my iTunes woes with a Unix/Mac-knowledgeable friend, and he mentioned something about fonts, albeit related to a different issue he read about online.
This mention of fonts reminded me that last week I noticed that iTunes was using Curlz for the information pane of podcasts. Last night, I decided to look into the Curlz issue, and a spotlight search revealed that I had two copies. I deleted the Office/Fonts version of the font, and voilá... iTunes and CS3 now work. (For good measure, I cleaned my font caches and made sure that there aren't any other duplicates/conflicts.)