I have Jessie running on a Toshiba laptop with an i7-5500u processor and Intel HD 5500 graphics. My window manager is KDE 4.14 with the Plasma interface.
As long as I'm working everything is fine but when the screen locks after a time of no interaction, the desktop does not come back up: 1. when the session is set to suspend (in System Settings -> Hardware -> Power Management -> Energy Saving) and a key or mouse press is supposed to bring the session back, I get the (purple) background screen and a mouse pointer, but there is no response to key or mouse presses. 2. when the laptop lid has been closed, a black screen with a mouse pointer appears and no interaction is possible. The default action for suspending the session after inactivity, and also for closing the lid, is "Sleep". If I choose not to suspend the session on AC power, then after inactivity the screen still goes blank, but the session comes back after an interaction. The problem seems to be the "Sleep" setting for inactivity of closing the lid. Does anyone know if this can be fixed other than by deselecting "Suspend Session"? Previous posts about suspend/resume problems with KDE seem to have to do with nvidia drivers. I don't used those though, as I have an Intel card..
