Should not be a problem , make sure you are using the correct image , the 3G takes it own special image . Also make sure the rommon is up to date for the image you are trying to use . And last you need enough space in bootflash to download the image . Squeeze bootflash to create enough room , if not enough room then you would need to delete the running image and squeeze the space and download the correct image then change your boot statement . What is the message that you get specifically ?
