cannot redeclare theme_signup_user_schedule()

This is similar, but NOT a repeat of http://drupal.org/node/169372. I have received this note several times on my test site as I try to load/reload new pages, specifically the homepage when logged in as the admin:

Fatal error: Cannot redeclare theme_signup_user_schedule() (previously declared in E:\xampp\htdocs\drupal2\modules\signup\signup.theme:11) in E:\xampp\htdocs\drupal2\modules\signup\signup.theme on line 19

It appears to be a problem with signup.theme calling "function theme_signup_user_schedule". However, I am not versed in how to fix this. Please advise...

Thanks.