Are you using any sort of caching plugin, or do you see a “Clear/Purge Cache” button in your Dashboard or admin bar? If so, would you please try clearing the cache?
If that doesn’t work, or you aren’t running a cache plugin, try deactivating all plugins. If that resolves the issue, reactivate each one individually until you find the cause.
If that does not resolve the issue, try switching to the Twenty Fourteen theme to rule-out a theme-specific issue (theme functions can interfere like plugins).
It is difficult to be sure, because the fault is intermittent, by impression is that iThemes Security is the culprit.
Hello,
You are always able to temporary disable the iThemes plugins using the WordPress back-end and then to test the admin page.
If you continue to experience the same issue, please verify that the PHP version is at least 5.3.
You may also test the admin environment from a different machine to make sure that the issue is not related to cache of your browser.
Do you have access to your server error logs? If so, it might be helpful to check your server error log as soon as you encounter the blank screen next time.
I haven’t had the problem since deactivating iThemes Security, so there doesn’t seem much doubt that it was the culprit.
Fortunately I have got a long password, with plenty of arbitrary characters in it.
Excellent, you might want to post over at https://wordpress.org/support/plugin/better-wp-security just so they’re aware of the issue.
