Can see menu on left in WordPress backend, but not the main screen

After I login to WordPress, the screen shows the regular menu options running down the left hand side, but the main part of the screen is completely blank. When I click on the main options: Posts, Appearance, Plugins, etc. the rest of the screen stays blank.

Once logged in, I can go to an active post on my page, eg and click “Edit this Entry”, which brings me to the corresponding page in the WordPress backend, but again I cannot see the data. It’s still a completely white screen, except for the menu options.

I tried to upgrade WordPress by clicking the prompt, but this didn’t work as again I could only see a blank screen.

I would really appreciate any help that might be available. Thanks.

My first guess would be a theme conflict, although that usually doesn’t effect the admin side. I would try switching back to the default theme and see if that clears the problem.