I have users who also experience this. The workbook has 21 sheets at the bottom, each page has three pie charts (black and white). The user was trying to highlight the text next one of the pieces of the pie chart to change it to bold. They then received this error, rebooted, received it again. They then worked in Word for 1 hour and went back into excel and were able to complete the task. This is a recurring issue that I need to resolve for this department because they have critical deadlines. The users have compaq 733's w/128 ram running NT4.0 and office 97. Could the size of the document have anything to do with it?