3435240 - Excel Addin Logon error: "Invalid User or Password"

While logging into the Excel Add-In an error occurs, "Invalid User or Password"

SAP Business ByDesign

1. Open Excel
2. Logon to the Plugin with a user name which contains i.e. characters like ś 
3. The error appears

While special characters like ś or similar characters as in Spanish, French or east European languages can be used to logon to the browser itself, Office and Excel and Outlook do not allow such characters in User ID to logon.

1. Open the work center Application and User Management
2. Go to Business User view
3. Search for the user and change the User ID to standard characters

The User Name still can use such special characters.

Excel error, Logon Error, Password and User. , KBA , SRD-CC-OIN-XL , Excel Integration , Problem