Photocrati NextGen Gallery causes white screen

Dear all,
I have been using wordpress for years now to write my family blog. It has always been running flawlessly – thanks to everyone who works on this great platform!
Now the issue:
Wordpress 4.4.1
Theme Twenty Twelve
Suddenly (after writing numerous blog posts with both use of wordpress media gallery and NextGen (I like the Slideshows more), the blog gave me the WSOD (white screen of death).
I managed to deactivate all plugins via the Ipad app (could not get access anymore, though, through the wp-config.php on the pc). The cause for the white screen definitely is NextGen Gallery as all other apps upon reactivation let the blog work just fine. As soon as I activate again NextGen, WSOD.
I would like to continue to use NextGen as I have used it extensively in the past. Without it, I will have to change a whole number of posts.

Any advice is highly welcome.

Thanks so much!