Would need to know a few things:
1. Is the member dashboard not showing JUST for you (the admin)?
2. Create a test account at your site (non-admin) and see if you get the error on the dashboard as well.
3. Did you manually add anything to your dashboard page via Studio?
4. Did you recently install any new modules?
5. If both #1 and #2 display an error (blank page), try going into your Studio > Pages Choose Dashboard from the drop down menu. See what blocks you have enabled there. If multiple boxes, try disabling one at a time to refresh the page to see if the error goes away.
6. When all else fails, you can set your display_errors to ON in your php.ini file so that the actual error will display instead of a blank page. This will help tell you what is wrong.