If I go to a bug page and change its product using the drop-down menu, then I can hit the "edit" button next to component to change its component. However, if I hit the "edit" button first, realize the component I want is not there, and then go and change the product with the drop-down menu, I can no longer get it to change the components list to the right one for the new product.
The way to change products and components in bugzilla is to do the following:
1- in the bug page change the product to whatever you want from the product drop down menu.
2- click the "Save Changes" button this will take you to the page with the list of the components for your new product.
3- in the new page for "Verify Version, Component, Target Milestone" you can select the component you want and then submit.
it is this way because for each product the product details are different and that is why you go to the new page where it load all those details for you.