Excel column names include file name

[#1]

This question is related to other issues. One thing always leads to another...

As a solution to a problem I decided to split my Excel into two seperate files with different data.

This second file has a different name of course.

After imprting this file into my personal files and using it in a worksheet, all colum names have the file name as a prefix. This way I can't see the column name in the drop down so I had to rename all column manually (remove the filename).

Is this a bug or am I doing somethig wrong?

I hope the image illustrates my problem.

To make things worse (for me): after renaming all the columns the problem still exists and even after deleting the original file, I can still see the columns from the original file. What am I doing wrong? How can I solve this and how can I prevent this in the future?

Thanks.