I have gotten achy legs (and sometimes arms) off and on my whole life. Its a deep ache that runs through my legs..I dont know if its in the bones or just buried deep. I realized when I was little that I would get achy legs whenever I had drank coca-cola. I could drink any other soft drink (an even caffine-free coca-cola) and not react, but after a regular coca-cola I would get achy legs.
I read some where that this achiness could come from dehydration in your muscles, and i noticed I get it now sometimes after a hang-over...usually when im dehydrated.
Im not sure if this is the same thing as what you all feel, but watch your diet and see if you notice a chain in the achiness and something you eat/ dehydration.