require_once failed to open stream

Hi, I am writing a plugin to create an archive menu. Everything works fine on the web server I have on my computer at home, but when I try to enable the plugin on the website with my web hosting provider, I get the following error from the ‘load_template’ function:

Warning: require_once(/hsphere/local/home/openfig/barefootfool.com/wp-content/plugins/barefoot-archive-tree/bf.BareFootArchiveTree.php): failed to open stream: No such file or directory in /hsphere/local/home/openfig/barefootfool.com/wp-includes/theme.php on line 1115 Fatal error: require_once(): Failed opening required ‘/hsphere/local/home/openfig/barefootfool.com/wp-content/plugins/barefoot-archive-tree/bf.BareFootArchiveTree.php’ (include_path=’.:/hsphere/shared/apache/libexec/php5ext/php/’) in /hsphere/local/home/openfig/barefootfool.com/wp-includes/theme.php on line 1115

The file with the plugin information header is:
barefoot-archive-tree.php
which uses ‘load-template’ to load a class, Barefoot_Archive_Tree (class extends WP_Widget), in the following file:
bf.BareFootArchiveTree.php

I add the action with the following code:

add_action( 'widgets_init', create_function( '', 'register_widget( "Barefoot_Archive_Tree" );' ) );

I have verified that the file in question does exist on the web host, and none of the other files that I include/require with load_template give me an error.

I can get the plugin to work through my web host provider by moving all of the code for the Barefoot_Archive_Tree class into the barefoot-archive-tree.php file. But I use load_template is other places in this plugin’s files & it works file!

I can’t figure out why I’m getting the error. Does anyone have an idea?

Thanks in advance,
Dan