If you have never run the EndNote program under the account you're currently logged in as, you may get an "Invalid Class String" error when you try to use the tools in Word. To fix this:

1. Close Microsoft Word (and Outlook if running).
2. Open the EndNote program and a library.
3. Open Word and try to use the tools.
4. They should function as expected.

You only need to open the programs in this order the first time in order to establish the link between Word and EndNote properly.

You may also get this error if the program was installed under a different account than the one you are currently logged in under. On a Windows NT/2000/XP system you must install the EndNote program while logged in as the user who will be running the program, and this account must have administrative rights to the local machine in order for the registry to be updated correctly. Rerun the installation under these conditions and the error should be resolved.

This error may also be caused if you are using a different version of EndNote than the version of the CWYW tools that are installed in Word. Make sure that the version of EndNote that's currently open matches the version of the tools in Word when you go to "Tools > EndNote". The name of that "EndNote" submenu should be EndNote 6, 7, 8, 9 or X.