New Custom Control for Team System will allow you to perform Spell Check on any field inside the Work Item. Support all languages.

This TFS Custom control for Work Items (requires SP1) allows setting a parent work item, displays parent work item as well as a child hierarchy and prevents closing a parent when any child work items are not closed. Known Issues: As with any TFS custom work item control, this does not function from within TFS Web Access (TeamPlains).