Melanie,
it seems to be a bug with the “Default Product Sidebar Config” setting as the Pixelix pointed out. I have the same issue.
I select on the theme setting page “Default Product Sidebar Config” & “Default Product Left Sidebar” & “Default Product Right Sidebar”, see the attachment.
Then when I check the product page, let us say produkt “Blue carpet”, the product page has the sidebar BUT as soon as I update something on the “Blue carpet” product page (for example change the price or ad some attribute, what ever) AND press the Update button the sidebar disappears.
I checked the custom fields (sf_right_sidebar, sf_sidebar_config, sf_left_sidebar) and noticed that after when a product is updated the Product Meta fields OVERWRITES the “Default Product Sidebar Config” settings and saves the default per page EVEN you don’t change the Sidebar Options->Sidebar configuration-> No sidebar (NOTE wrong help text here…Choose the sidebar configuration for the detail page of this portfolio item.)
And the result is… the custom field “sf_sidebar_config” get overwritten with value “no-sidebars” which is not correct and NOT wanted and makes the sidebar suddenly disappear 🙁
Please forward this ti Ed to take a look at and the solve the obvious BUG!
Thanks