Can't get Jetpack to work with my multi site

Hello,

i have a problem with WordPress Multisite. When I install Jetpack on my Network two of my Sites get broken. In fact after installation of Jetpack and after activating it for the entire network two of the sites are broken. Broken means that when I go to wp-admin of those two sites then I get an empty page (browser doesn’t display anything anymore). Then I delete Jetpack from ftp and then all works again. However I would like to get it work with Jetpack. So what I have done is I deactivated other plugins for that site and went through the installation proceedure with Jetpack again and then checked. Well that way at least I could fix some other sites but nevertheless I am stuck with two sites just showing blank after activating Jetpack.

What can I do to fix this? Thank you very much in advance!