Unable to read user name

Hi,

I have used the following code to read the user who has logged into the portal. However my WDJ application fails to return the user name for one particular user. Any suggestions ?

		IWDClientUser wdClientUser = WDClientUser.getCurrentUser();
		IUser sapUser = wdClientUser.getSAPUser();
		if (sapUser != null) 
		{
			IUserAccount[] acct = sapUser.getUserAccounts();
			if (acct[0] != null) 
			{
				String strUserName = acct[0].getDisplayName();
				strUserName=strUserName.toUpperCase();
				userID = strUserName;				
							
			}
		}