item file upload but not importing

Successfully uploaded new item file IIF, and can find in UPLOAD directory, but when I import, I get an instantaneous "your data has been imported" pop up box. But of course new item file has not been imported. Old data still exists. Knew there would be a problem s it takes time to import the data file. the process is not instantaneous. Am I importing incorrectly?I'VE GOT IT WORKING NOW. but question remains...when updating the item data file, I 'discarded' the first 10 lines so i could just work in the item data lines more easily. when this respective IIF file would not import correctly (see above). I cut and past the top 10 lines back in again again, like the original file, but still did not upload. This when i wrote the above problem. Now I downloaded the original item file again, did not cut anything, just overwrote the item lines with the new data. uploaded and imported with out problem (yah!). Obviously cannot cut and re-past the top 10 lines then save as txt and then IIF without importing problems. But why, everything looks the same as the original 10 lines...?