When I try to start Word X, it gets as far as the splash screen and then dies. The splash screen I could do without; Word itself I can't.
If you've been trying to guess what's causing this problem, stop now. Chances are, you haven't come up with a font filebut that's most likely what it is. A corrupted font file, a duplicate font file, or both together can cause Word to crash on startup.
Tackling this problem can be a little tricky, because the guilty font can be located either in one of the Mac OS X fonts folders or in the Classic Fonts folder (/System Folder/Fonts) if you have System 9 installed. Proceed as follows:
If there's an update to Word X that you haven't installed, install it immediately. See if that cures the problem. If not, carry on with the steps in this list.
Switch to the Finder. Open a window to the Classic Fonts folder (in the /System Folder/Fonts folder on your hard disk). Next, open one window to the OS X shared fonts folder, ~/Library/Fonts, and another window to your fonts folder, ~/Users/<your_user_name>/Library/Fonts. Line up the three windows so that you can see the contents of each, and delete any duplicate font files. Once you're confident you've deleted all the ringers, restart Mac OS X and try launching Word. If Word starts, all is well. If not, go to Step 3.
Still with me? That's a pity. Next, you must find out whether your Mac has a corrupted font menu cache. If your Mac has System 9 installed on it, restart in System 9, either by using Startup Disk (choose Apple » System Preferences, click Startup Disk, choose the System 9 startup disk, click the Restart button, and confirm your choice) or by starting from the System 9 CD. In the Finder, open the /System Folder/Fonts folder and see if it contains any fonts. If it does, rename the folder OldFonts or another distinctive name. Reboot, and then try starting Word. If it starts okay, create a replacement Fonts folder, drag all the fonts from the OldFonts folder into it, and delete the OldFonts folder. Reboot again, and try starting Word. If Word crashes again, go to Step 4; otherwise, you're off the hook.
Still in System 9, create a folder called TempFonts on your Desktop. Open the /System Folder/Fonts folder and drag all its contents to the TempFonts folder. Reboot into Mac OS X and try to start Word. If Word starts, one of your Classic fonts is causing the crash. To find the guilty party you'll need to restore the fonts from the TempFonts folder to the Fonts folder one by one, rebooting and testing Word after each one. When you find it, delete it and then restore the remainder of the fonts. If Word doesn't start, repeat this step first for the ~/Library/Fonts folder and then, if necessary, for the ~/Users/<your_user_name>/Library/Fonts folder, until you have eliminated the offending font.