It sounds like what you are doing is the correct procedure. The Ignore All attribute can be invoked in either of 2 ways:
- When running the main Spell Check, using the Ignore All button, or
- Right-clicking the term in the document & selecting Ignore All from the contextual menu
Both remove the red underlining from all instances of that specific spelling. Also, any new entry of that same spelling should not have the underlining applied, nor should the flagging of ignored terms reoccur when the document is opened again [unless the checking is reset]. If that isn't the case I'd recommend confirming some basics before any further troubleshooting:
- Make sure Office [14.2.5] & OS X are fully updated
- Run Disk Utility to repair disk permissions on your HD
- Restart your Mac
If those steps don't remedy the problem please supply any additional details when you reply. For example, it would be helpful to know;
- If the problem is with one specific document as opposed to all
- Whether Track Changes is used in the document
- What format the document is saved in
- The origin of the document
- What happens if you use Add rather than Ignore All