I installed uc_event too and I got exactly the same error Katrina had when trying to add an event to the store (see below). It did add the event only partially I think. When you list the products in the store they are mentioned at the bottom of the list-page but not anywhere else (e.g. catalog). When going to the added event it does list price etc. but 'add to cart' button.

(warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, 'uc_product_add_to_cart_form_1' was given in /home/vol1/byethost3.com/b3_2064628/htdocs/drupal/includes/form.inc on line 218.)

Thanks a lot,

Wouter