I have the identical problem with my PB G4 15-inch 1.25 GHz for about one month, and it is getting worse. My screen info from System Preferences is identical:
Manufacturer: 00000610
Model: 00009C20
Serial Number: 00000000
Manufacture Date: B87B9680
When it started, I noticed that changing the display angle made problem go away (it being an almost complete fadeout to a light blue, with some vertical lines, desktop not visible). Re-start/Startup behaved normally in terms of chime, etc, but no desktop visible in the faint blue image. I assumed that it was a hinge problem. As it worsened (I see more intermittent black full screen or partial screen black rectangles), I had some intermittent luck with VERY SLIGHT flexing (I know, the LCD is glass) of upper case at upper left corner (BTW, no damage or dent there, I treat this out-of-warranty PB with love, care, and lots of cushioning when travelling). After this started, my daughter spilled some soda (high fructose corn-syrupped pop in the midwest) on right keyboard, yielding sticky keys. Being comfortable with electronics (after all, it was built by other humans) and out of warranty, and having reason to do so, I disassembled lower case, removed keyboard, washed thoroughly with distilled water, dried with compressed air, and let dry overnight). While disassembled, I looked over hinge and wires to display and saw no damage, sticky goo, or anything consistent with hinge or lower wire involvement with display problem.
At this point, out of frustration, I removed top bezel in order to expose back of display. The Samsung LCD is an LTN152W5-L02, serial no. UJ347XDXQ8WA; other nos. on label are: 0348 4J3K11517H 010. On the circuit board to which the display contacts are affixed, a label says: T00798C33K0018. A label on the white backlighting, probably not relevant but listed here for completeness: LJ96-01519A 152W5-L02 ST1031121DY05810.
I see no damage anywhere I can look on back of display (I did not probe the white tape areas along top and left edge, heeding the warning label for this sensitive area; why push my luck?). The ribbon cable is OK and firmly connected. At this point I searched the web and found this thread topic. I am probably going to try the slight-pressure approach (beats holding the display corner while using the PB) recommended by "bryanus" post of 10/23/06, in my case with self-sticking velcro fuzzy tape strips placed on the aluminum top bezel at spots corresponding on the display back to where I have success in restoring the display function by pressing.
With the display back off I can get the desktop to reappear when lightly pressing on the upper left corner. It is more likely to work if the computer is warmed up to room temp, with more problems and less success if the computer is near a cool breeze by a window where I work. The laptop does not run hot. As others noted, I had no luck with underwear maneuvers.
My pseudo-intelligent guess (Chemistry PhD, so my "knowledge" is piled hip-deep) is that there may be one or more bad batches of LCDs from Samsung where the LCD glass-to-electrode contacts are somewhat faulty or prone to failing with aging or normal wear and tear. This would explain how pressure can restore function, and why temperature affects performance since glass and metal have different thermal coefficients of expansion.
I am a Mac user from back in 1984 with first Mac 512K, and have owned a number of them over years. Weathered the bad times (and gibes from PC afficionados for my using a computer named after a fruit) before Jobs reappeared and saved the company. My few interactions with Apple repair have been excellent - they once replaced the LCD on this PB outside of warranty for free when I pointed out that I had just read about the white spots on some displays in the PB's early production runs (gotta get out of my lab more often!) and had a few of my own that I assumed were natural for LCDs of that era; Apple even replaced bottom case piece at the same time at no cost. Led me to buy stock in the company.
I am new to discussion threads, so if anyone has other info to pass on, or any response from Apple Corporate to this presumably rare display problem, please pass it on. Thanks!