Hey,
Yeah, I got those display issues when using a resolution that the LCD didn't support.
When it boots, there is a 3 second delay during which you can interrupt the boot sequance by pressing a key.
Then, at the "WMT # "promptyou can set the desired resolution for VGA and HDMI by typing these commands:
setenv wmt.display.param 4:0:0:1280:800:60
setenv wmt.display.param2 4:6:1:1280:800:60
(I needed the resolution to be 1280 by 800 obviously, and 60 is the screen refresh rate)
Then save these settings permanently with the command:
And reboot the board.
I think I found these instructions in a script that writes a scriptcmd for an Android image some time ago (can't remember where though).
If you can't connect to the board via UART but you know how to compile a scriptcmd to boot the OS, you can add those commands there I think.
Let me know in what way you fix it, that would be useful information for everybody I think.
Michaël