My son has R4 VIII and this works fine with a 4gb microsdhc card. I have got myself an r4SDHC (different r4, sometime called r4 version 3 which is different to r4 VIII, confusing I know!!!) am waiting for my 8bg sdhc card to arrive in the post as the r4sdhc is suppose to support up to 32gb card. I will let u know if it works but just remember that each version of the R4 requires different software (kernal) to make them work as if I put my son sd card in my r4 it doesnt work and just says loading because the software needed is different. So maybe if u are having this problem make sure you have exactly the right software for the r4 that you have. Cheers