Phone issue pic

Had to link to another site to post pic because maximum file size here is 2 bytes. That's useless.

Anyway, please look at the pic and let me know what you think the most likely cause is. When the display looks like this, functionality is limited. Cannot place calls on hold, etc. Issues occurs on multiple phones across multiple port cards. Re-booting phone clears it up sometimes, other times it resolves on it's own.24 key phones and 48 key phones, all digital.