This is a resolved problem, but I wanted to post it for the benefit of future mp3car-ers. (And to feel like I didn't waste an afternoon trying to figure out what was going on.)
I have a Lilliput 619GL-70NP which had been giving me greef over the past month. VGA inputs were not responding, the screen would randomly fade to white, and eventually (after pulling everything apart and reconnecting it) colors with low saturation would pretty much merge together. The odd part was that I did not lose any colors, but it just looked like the screen was showing 256 colors, while the computer was outputting at 32-bit. (It wasn't actually showing 256 colors, but it was just that crappy.)
Pictures to make this make a little more sense: (This is a screen cap of what was actually being displayed. I just opened Microsoft Paint and double-clicked on a color, then chose Define Custom Colors. This gave me the full color palette.)
Here is a digital camera snapshot of what it looked like on the LCD:
Notice that as the colors get less saturated, they blend together. However, not a single color is lost, so it's not like I've just lost all reds.
Anyway, to the solution! I found the ribbon cable connecting the actual screen to the circuit board was the problem. Even when it was placed in properly, the metal contacts on each end of the cable were actually peeling away. They would fold back and either not make contact, or possibly cause a short with their nearest pin.
To resolve this, I just took a pair of scissors and very carefully cut off the tips of the cable. I ended up taking off about one-fifth of the actual bare metal contacts. When I slid the connector back in and fired the screen up, SUCCESS!
Now, I've heard it noted here before that DigiKey (among others) sells this cable. Supposedly, it is Digikey Part Number HFF-40U-06-ND. Be aware that Digikey charges a $5 handling fee for any order under $25, so if all you need is this cable, I would advise you to try trimming the tip before you spend $15 (and a few days waiting) on a replacement.
Hope this helps someone!