4 days ago I upgraded to WP 3.7.1. I also upgraded my Weaver II theme at the same time but it stopped working properly too. So I purchased PureView from MyThemeShop which worked better except for having thumbnail issues. Yesterday I installed Ziplist plugin and SEO by Yoast plugin. Was okay until I started using the Yoast plugin. Then I suddenly couldn't see menus and things. I then deactivated the Yoast plugin, but couldn't just click on 'deactivate' (didn't work), so had to select and then choose deactivate from the drop-down menu. It hasn't fixed anything though. When I clicked on a post or page to edit it, it would take me to the screen that lists all of the posts. I also couldn't get to edit plugin page or the page to edit my theme.
This morning I tried changing the theme to Twenty-Twelve (as suggested in other recent posts), but it wouldn't change the theme. Now my Dashboard is completely weird and just looks like weirdly formatted HTML and I can't do anything with my site. Yet the website itself is still working fine, I just can't do anything to update it.