importing MT

Just as an aside, I have read some of the previous topics on the subject, but I don’t feel as if they answer my question.

I changed the import-mt.php file to reflect the txt file name of my import file, and when I click the ‘Let’s go!’ link to proceed, I get:

The file you specified does not seem to exist. Please check the path you’ve given.

and it tries to access the link :

wp-admin/import-mt.php?step=1

I don’t know how to address this problem in the slightest. Help would be much appreciated.

Thanks,
Catherine