I've cleared the data files, made sure the Write Data as Text box was unchecked, and I've had the same problem. The numeric data are written in the Excel file, but I get a series of error messages (about 40 or so) at the end of running the experiment. I get these on four (out of 8) questionnaire files, one for each variable in the file.

I'm running ML 2008.1.33 on a Dell machine (3GB Ram, 2.13 Ghz Intel chip) with Windows 7 Home.