It looks like the links that are broken are trying to open a javascript/JQuery window to display Google Calendar events. For example, clicking on the Tuesday Meditation Class at the top of the left column. However, if you click the links at the bottom of the page that go directly to content, like Transforming Pain, it goes to the content item and seems to work fine.
My guess would be that one or more of your plugins or your theme is misbehaving, either of which might explain both problems.
I think I’d start with the plugins. Since you can’t access your plugins page and deactivate and test your plugins, I think I would deactivate all your plugins, then reactivate them one at a time until you can find the culprit(s).
To deactivate all the plugins without access to the admin side, access your site via FTP or using the file manager for your hosting account and rename the /wp-content/plugins folder to /wp-content/plugins.deactivate, then log in to your admin side. Go to the plugins page, and you will get a scary message about all the plugins being deactivated. Use FTP to rename the wp-content/plugins.deactivate folder back to wp-content/plugins and then refresh the plugins page.
Reactivate the Google Calendar Events plugin first, and see if the links work to display the content without the error. Then reactivate one plugin at a time, testing your site each time to determine which is causing the problem. Unfortunately, you may have to test combinations of plugins because it may be two interfering with each other.
If the Google Calendar Events plugin doesn’t work by itself with no other plugins activated, try a default theme and see if the links work. If they do, it’s probably an issue with the theme and Google Calendar Events. If they still don’t work, it seems like it would be an issue with Google Calendar Events itself.
