Hi all, long time lurker first time poster. I've got a Mac pro 4.1 2.26Ghz that has been flashed with 5.1 firmware. The issue is that I've just installed a flashed XFX HD 5770 like this one to use as a back up card and it all works fine apart from the mini display port. I get the apple logo and boot screen on both of the DVI ports and when plugged into the mini display port with an apple mini display port to DVI adapter. However once booted to the login screen the mini display port goes black. DVI ports are working fine. Any ideas? Happy to use the DVI but just interested. Assume it's something to do with something being loaded once the machine has booted? It's attached to an old 23 inch apple monitor. Thanks for the help.