Hi. Thanks for reporting.
I just tested this and was able to install and access the WP Google Fonts plugin with 3.6. However, I didn't have the plugin installed prior to this.
Can you try the following, from the master list for troubleshooting 3.6:
- flushing any caching plugins you might be running, as well as server and/or browser caches.
- deactivating all plugins (yes, all) to see if this resolves the problem. If this works, re-activate the plugins one by one until you find the problematic plugin(s). Sometimes, an apparently inactive plugin can still cause problems. Also remember to deactivate any plugins in the mu-plugins folder. The easiest way is to rename that folder to
- switching to the Twenty Twelve theme to rule out any theme-specific problems.
- manually upgrading. When all else fails, download a fresh copy of the latest.zip file of 3.6 (top right on this page) to your computer, and use that to copy up. You may need to delete the wp-admin and wp-includes folders on your server. Read the Manual Update directions first.