[OS X TeX] Suddenly, I'm Italian

[Enrico Franconi]

>> Looks like you are using a combination of TeXShop's Command Completion (e.g., \be+TAB --- you appear to have set TAB as the trigger) and Apple's Completion (e.g., definit+ESC). 
> 
> In TS's preferences you can choose either ESC or TAB to trigger command autocompletion. No matter which one you choose, def+ESC will open Apple's dictionary but def+TAB will not. 

In "System Preferences", "Language & Text", "Text" you can choose the default language for the centralised dictionary used by Apple spelling. Maybe you have chosen the "Automatic by Language" option, and the system got confused by the text you already had and started proposing Italian completions. Once you had enough English words in your text, the automatic system eventually understood you were an English writer.
cheers
--e.