[Plugin: Chatbox] Error Message

This Chatbox test is with a fresh install of WordPress with the default theme and only a twitter feed plugin. After adding the widget to Appearance > Widgets > Primary Widget Area, I went to the live web page under Chatbox with the Post form. I typed a word and get Post. The following error was displayed on top on the Chatbox:

Warning: strpos() [function.strpos]: Empty delimiter in C:\wamp\www\wp-content\plugins\chatbox\chatbox.php on line 55
Call Stack
# Time Memory Function Location
1 0.0007 672976 {main}( ) ..\index.php:0
2 0.0013 677808 require( ‘C:\wamp\www\wp-blog-header.php’ ) ..\index.php:17
3 0.1490 21972320 require_once( ‘C:\wamp\www\wp-includes\template-loader.php’ ) ..\wp-blog-header.php:16
4 0.1500 21977776 include( ‘C:\wamp\www\wp-content\themes\twentyten\index.php’ ) ..\template-loader.php:43
5 0.1670 22068840 get_sidebar( ) ..\index.php:31
6 0.1670 22069448 locate_template( ) ..\general-template.php:92
7 0.1671 22069616 load_template( ) ..\theme.php:1062
8 0.1678 22094256 require_once( ‘C:\wamp\www\wp-content\themes\twentyten\sidebar.php’ ) ..\theme.php:1086
9 0.1678 22094344 dynamic_sidebar( ) ..\sidebar.php:20
10 0.1683 22098680 call_user_func_array ( ) ..\widgets.php:891
11 0.1683 22099080 WP_Widget->display_callback( ) ..\widgets.php:0
12 0.1684 22100112 chatbox->widget( ) ..\widgets.php:182
13 0.1697 22050016 strpos ( )