Cannot view posts when logged in

I noticed yesterday that now when I am working on a new post and I go to preview it. The preview page is not formatted right. It is missing my theme.

When I am logged in and my WordPress toolbar is displayed at the top of the browser, the same thing happens. So it seems that when I am logged into my site and viewing a page my theme is not working. When I am in the dashboard it is fine.

This happened after the last update I believe.

When I disabled Gallery plugin, everything is fine.

Can you help?

Thank you!