I had something very similar when I tried to change the theme. I downloaded 2 themes and had saved 1 as BMPO1 to distinguish them. Loaded it onto my player without taking out the "1" and all I got was the same screen as you. Could not access anything on the player at all.
To solve it I just did another update to v4.1 and it went back to the default theme and everything worked ok.
May not be the same as you, but thought I would let you know in case!
Sorry by time post...
My VX787 is in same conditions RED SCREEN... any bodi can sayme who fix it?
there are several great recovery guides by seasprite in the forum with all the tools needed to fix your player so do not worry, red screen usually means a corrupted graphics file BMP0, sometimes it can be fixed by opening the partition and replacing but the best thing to do is reinstall the firmware with the PC tools, all of which are available in seasprites guides