First of all, you don't need to add the <img> tag to the list of allowable HTML tags - Geeklog's image upload works without that (it shouldn't make any difference, though).
Are you getting any error messages when you try to save your story? Also check that you have a directory images/articles in your public_html and that it is writeable (775). And, of course, file_upload should be enabled in PHP.
That's about all I can think of. Usually, Geeklog will display an error message if something goes wrong and that would give us a better idea what the actual problem is ...
bye, Dirk