Dashboard giving 500 Error after successful wp-login. Site is up

Doing some debugging would help you get to the bottom of this.

To debug WordPress, see https://codex.www.ads-software.com/Editing_wp-config.php#Debug. For information on how to debug PHP see https://tim.oreilly.com/pub/a/php/2004/08/12/DebuggingPHP.html , https://www.ibm.com/developerworks/library/os-debug and https://www.xdebug.org/ . For multisite installs see https://codex.www.ads-software.com/Debugging_a_WordPress_Network as well.

Still having problems then:
Please disable or delete all plugins and switch to the default theme (TwentyEleven since 3.3). After making these changes does the problem still occur? If no, re-enable everything one by one to see which component causes the problem.

The site is running Headway Themes 2.0.13 and the following plugins (although because I can’t access the dashboard, they might not all be active):

• wp-tables-reloaded
• wp-fb-fan-box
• wp-db-backup
• twitter-anywhere-plus
• simple-image-widget
• sexybookmarks
• meteorslides
• gravityformspaypal
• gravityforms
• google-sitemap-generator
• font-uploader
• commentluv-premium
• akismet
• add-image-src-meta-tag