TWS users running add-on applications in Excel using DDE on a Windows 64-bit operating systems may receive the following error message upon log in or when enabling the DDE client:
Ddedll.dll file missing or out of date
If you are attempting to use the DDE API, please see KB2155 for assistance with resolving this matter. If you are receiving the message but not using the DDE API, please log into the TWS and select the Edit and then Global Configuration menu options from the top, and then the Global Configuration, API and Settings menus from the configuration screen. Then click Disable DDE Client.