1) You listed your installer version (Vicibox 6.01), which is nice. But it does not tell us which version of Vicidial was installed by it. This is always required: Vicidial Version with Build. It's in the bottom left corner of almost every Admin.php page.
2) There is a known bug with the lead loader, but I have not heard whether it affects all types of loading yet. My suggestion is to load the file with the Standard field order using Tab Delimited. (Always been the safest method of loading if you're having any problems). Click on the ( ? ) next to "Browse" when uploading your file. It'll give you the fields and the field order. Even though most of the fields will be empty, if you create the spreadsheet with those fields and save as tab delimited, the file can be loaded as "standard" and NO mapping is needed in Vicidial. This skips a major portion of the lead loading code ... and has always been error free.
3) Alternately, you can attempt to load using several data types and even using the old lead loader if there's a link on the page for it still.
Happy Hunting!