There a lot of people new to the RaspberryPi miss the explanation that although your Mac or PC can write an SD card if you then view it it will not read everything thats been writen.
The produced card has a Dos partition that the PC or Mac can see and a Linux part that cannot be seen.
This Linux part comes into operation when the RPi boots but if you RPi has some other issue (More than likely power allways suspect power) then even though the SD card is correct it won't boot. And if you return it to your PC or Mac the part that the RPi is going to use (it is there) Yor PC or Mac just won't see it.
In addition if you have used the Wheezy image it only installs a small section of your SD Card this allows it to be loaded onto smaller cards you then run part of raspi-config and this uses EXPAND ROOTFS to expand the root file system to use the remainder (unused portion) of the SD card.
In all likelyhood your SD is ok, the problem is probably power and there are a lot of threads on this issue.
Noob is not derogatory the noob is just the lower end of the noob--geek spectrum being a noob is just your first step towards being an uber-geek
If you find a solution please post it in the wiki the forum dies too quick