Different spin on the solution.
The reason I ended up on this string is because my father-in-law is having the same problem with his Dell Latitude. The explanation he got from his computer expert was as follows:
"The power supply of the computer sometimes retaines residual electrical energy which interferes with the "wake up" process usually initated by the opening of the laptop lid. The solution would be to unplug the laptop, and remove the battery for approximately 30 seconds"
This sounds like *bunk* to me as I have had a Dell Laptop for over 7 years and although I have had to wait a long time sometimes for "wake up" especially out of " Hibernation Mode" but never had it where it just would wake up. However I have had it where because I use and "extended desktop" function and that after I have undocked, I have had to use the "Funtion+F8" key combination to switch back to LCD screen only.
Any comments are welcome.