Since you said the exact same sheet works perfectly on another computer, this makes me think the problem is outside of the sheet. I use Office 2003 and the Excel 2003 DDE works fine with the latest version of TWS so that is strange. Do you have an extra computer or laptop you can test with? Can you try installing the office that is on the working computer? Try to update your environment to match the working computer. Good Luck!
Anyone knows how to get RTH open, high and low for es? accxxxx|tik!id0?high gives me the high of the day, and open doesn't work.