Since a few updates and as well live-media, i could not boot into xfce manjaro stable any more (installed directly on hardware or using live-media). This problem was persistent for standard xfce live-media as well (at least I can state this for 17.1.5 and 17.1.6).
It seemed that it was not a kernel problem, no matter what kernel I used (I tested 4.9,4.14, and 4.15) I had the same problem. The only way i could boot into xfce desktop is using the catalyst driver and old xorg.
The behaviour of my pc:
grub (the bootloader) loaded well, i chose any of the manjaro entries and then it was like my computer fell into sleep before starting X. No messages, nothing. I even could not switch to a tty, keyboard was dead. The only thing I could do was cold-start my pc.
Cause: PCI express 2.0 seems to be working unstable for my graphics card (amd/ati radeon hd 5770) and mainboard (Foxconn A7DA 3) combination. This seemed to be not a problem for me until some things changed in xorg recently. According to the archlinux wiki this could happen for other ati graphics cards and mainboard combinations as well.
One solution is to reinstall using catalyst (proprietary graphics driver) which needs older xorg 1.7. However, then you are stuck with old software and an unsupported graphics driver.
A better solution is the one provided by pixel27: Deactivate the version 2 mode of the pci express port by using the kernel parameter
radeon.pcie_gen2=0. The following instructions helped me to use the kernel parameter: https://wiki.archlinux.org/index.php/Kernel_parameters.