The following programs are attempts to word 2013
Solution three kinds:
1, change the registry
HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Word\Options
Point to "New" and then click "DWORD Value." Select "New Value # 1," type UndoHistory, right-click "Edit." In the "Edit DWORD Value" dialog box, click the "Decimal" under the "base." In the "Value" box, type a value between 0 and 100, typically 20 enough, click "OK"
2, modify the active state of the input method, after this attempt does not work, restart and then re-check the word
3, add-ins, delete the COM add-ins and feasible.
Operation Path: Options -> Add-ons -> Go
The add-ons can be deleted.