Having difficulties booting would mean that your SD Card is written the way it is supposed to be and the OS starts loading but doesn't proceed and most certainly doesn't prompt you for logging in.
How do you solve it?
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Perceived SD errors are often a result of poor power supply. I would check the voltage between TP1 and TP2 pins and if it is below 4.5V, use a better cable or a better supply.
If you have network cable attached but the LED is not on (or going on and off), it is almost certainly a power issue.
A good cable is VERY important. If it is of poor quality, the voltage drop is too high.
Your SD card doesn't contain a bootable image.
Not efficient power supply
Raspberry Pi's power requirements are as follows:
Make sure you choose a charger (power supply/adapter) which meets those requirements and also
DO NOT TRY to power up your R-Pi using your computer's USB because it can provide no more than 100mA
Using a non standard SD Card Linux is well renown for working slow with UHS-1 SD Cards. Actually in Raspberry Pi that's is not a problem because the ARM processor handles it appropriately. Well you still need to add some patches to the kernel on the SD Card. Follow these steps:
*Note: You will need a Linux or Mac OS X to change the filesystem on the SD Card since it isn't readable by Windows! *