Before I start replacing parts in my computer to try to fix this, I wanted to check to see if this problem is more widespread. Basically, the wifi on my 5,1 doesn't work after the computer goes to sleep. If I turn wifi off, then back on... it works normally again. Otherwise, the computer has been and remains rock-solid. I know others have had graphics card issues with NVIDIA after sleep, but I can't find anything written about this issue. Is anyone else having this happen? Any solutions? I don't mind grabbing another wifi card, but I'm not sure that will fix the problem. I'm not really looking for an upgrade - just to have it work properly again. My setup is as follows: 10.13.4, 5,1 (native), 2*3.46 6 Core, 48 GB DDR3 (8*6), AMD Radeon HD 7970 3GB (MVC), wifi card is Airport extreme (stock card shipped with computer).