wordpress An internal server error occurred. Please try again later. safari

Since yesterday I am getting the error ' an internal server error occurred' when attempting to go into the admin dashboard - but only on Safari. I can do everything i need to do from Firefox.

It coincided with adding in a wp-photo gallery plus plugin which i have subsequently removed - but I can't work out why it's only occurring in Safari. I have cleared the cache, closed & opened it several times but the problem persists.

http://www.slade-tonbridge.co.uk i have granted support access fiat the wpmudev tab.