[Plugin: Calendar Plus] php error

Actually using WordPress 3.0.3 with the iThemes Builder theme. I’ve already contacted iThemes as you’ll see it suggests in the text below and they confirmed that the problem is with the Calendar Plus plugin.

Below is the error message I received when I tried to activate the plugin.

Fatal error: Cannot redeclare deal_with_deleted_user() (previously declared in /home/sacramen/public_html/wp-content/plugins/calendar/calendar.php:64) in /home/sacramen/public_html/wp-content/plugins/calendar-plus/calendar.php on line 73
Fatal Error (hide)

The theme has encountered a problem that it cannot recover from. Please use the following information to try to resolve the problem.

Error Code:
php_code_error:64:/home/sacramen/public_html/wp-content/plugins/calendar-plus/calendar.php:73:Cannot redeclare deal_with_deleted_user() (previously declared in /home/sacramen/public_html/wp-content/plugins/calendar/calendar.php:64)
Message:
A fatal code error occurred.

If you are unable to fix this problem, please copy all the text on this screen and send it to [email protected].

Debug Data:
Array
(
[0] => Array
(
[file] => /home/sacramen/public_html/wp-content/themes/Builder/lib/classes/it-error.php
[line] => 121
[function] => fatal
[class] => ITError
[type] => ::
[args] => Array
(
[0] => php_code_error:64:/home/sacramen/public_html/wp-content/plugins/calendar-plus/calendar.php:73:Cannot redeclare deal_with_deleted_user() (previously declared in /home/sacramen/public_html/wp-content/plugins/calendar/calendar.php:64)
[1] => A fatal code error occurred.
)

)

[1] => Array
(
[file] => /home/sacramen/public_html/wp-content/themes/Builder/lib/classes/it-error.php
[line] => 148
[function] => handle_error
[class] => ITError
[type] => ::
[args] => Array
(
[0] => 64
[1] => Cannot redeclare deal_with_deleted_user() (previously declared in /home/sacramen/public_html/wp-content/plugins/calendar/calendar.php:64)
[2] => /home/sacramen/public_html/wp-content/plugins/calendar-plus/calendar.php
[3] => 73
)

)

[2] => Array
(
[function] => it_error_shutdown
[args] => Array
(
)

)

)

Fatal error: Call to undefined method ITStorage2::_migrate_old_data() in /home/sacramen/public_html/wp-content/themes/Builder/lib/classes/it-storage.php on line 271