Translations:Problems & solutions/164/en
From LimeSurvey Manual
In order to perform multiple changes to your document with responses, you may choose to Export and open a file in Excel. Make changes to the data (other than the top two lines!) and then save the document as a .txt file. If you save it as .csv, Excel uses comma-delimits by default which cannot be imported back into LimeSurvey. By saving it as a .txt file, Excel saves the edited document as a tab-delimited file which imports back into LimeSurvey.