First thing to try: Go into Font Book and resolve duplicates (Edit menu -> Resolve Duplicates) and possibly also Validate fonts and files (from the File menu).
You haven't, by any chance installed or removed any fonts (Helvetica or variants) lately?
To change your language settings on a Mac:
Open System Preferences by selecting it in your Dock or the Apple menu (Apple > System Preferences).
Choose View > International.
Drag your language of choice to the top of the list.
Quit System Preferences.
Quit and reopen iTunes.
Hebrew isn't even on the list of languages for iTunes, and I removed the duplicate fonts aprat from Lucida Grande, which won't let me get rid of 2 duplicates.
I only have one suggestion left. As a last resort, you could try this! 😀
Actually, I do have another suggestion, after giving this more thought. It's possible you have a font corruption problem. If you want to remove the Hebrew font and save some space on your system, you can download and run Monolingual, a free app that removes unwanted language resources from your system.