I've had this problem with one of my rpi's, I formated the SD card and installed raspibian again. Now, the problem is in the other one. After the boot, the graphical enrivonment won't open, I can only see a - character blinking on the black screen, and nothing more happens. However, I can still SSH from my other devices. The strange thing is that control alt F1-F7 changes to new terminals for less than a second and start the black blinking - again. In one of the control alt F-something I can see the boot process and the
pi@raspberrypi:~$
ready for me to type something, but the black screen appear in less than a second in front of it