Hmm, it's hard to say exactly what's going on, but we can try a few things.
Does it work properly with a simple test file, such as seen at
http://listmailpro.com/help/import ?
"John","Doe","john@example.com"
"Jane","Doe","jane@example.com"
Are you on a Mac? Sometimes Mac users need to add the following to config.php anywhere between the first and last line (starting and closing php tags):
ini_set('auto_detect_line_endings', true);
It's odd because it appears ListMail is reading your file and checking the email address formats and finding them correct.
The problem is most likely with the MySQL query that inserts the users.
For v1.88, try changing line 796 of edituser.php from:
@mysql_query($cmd,$link);
to:
@mysql_query($cmd,$link) or die(mysql_error());
This should output more information in the event of a MySQL error.
Regards, DW