Can you replicate the problem using the default Twenty Fourteen theme with all other plugins deactivated?
Yes it does happen with Twelve Fourteen but I have done a lot of experimentation with activating and disactivating plugins. In some cases I had to re-name the folder for the plugin on the server to get WP functioning in the admin mode again. At the end of the day I have come to the conclusion that it is some problem between “Fast Secure Contact Form” and Akismet. If only one of them is activated everything works fine. If both are activated I either get a white screen if I try to customise a theme or, in some cases depending on which was activated first (I think) I get a white screen in all admin menu functions.
I will try a different contact form but I am starting to think I may be using the wrong system for what I want to achieve.
It would not surprise me if this incompatibility is actually being caused by some other plug in as I have most plugins that I am using working on other sites. The problem is that it is taking too long for me to sort out and I am going round in circles. Perhaps I should delete everything and start a new clean installation.
I’m really surprised to hear that these two plugins are conflicting. Akismet is used on millions of WordPress sites whilst the ast Secure Contact Form plugin is also very popular.
Try checking your site’s error logs for a more specific error message. Your hosts should be able to help you accessing your site’s error logs.
Problem resolved.
I deleted all the tables in the database and did a reinstall. The fresh install found all the plugins because I had not deleted the files. 🙂
When I re-activated all the plugins the problem had disappeared.
Obviously some problem in the database.
Thanks for the suggestions.