It seems that various sources say that M3 Lite can use SDHC 4GB for their media extend mode (mp3s, etc, in moonshell). If, however, you cannot boot up from your SDHC card, then either it is nor formatted to FAT, or it is possible that you are in possession of a 'fake' SanDisk memory card (there are a lot of them floating around), which is actually smaller but compressed to make double the space. As far as I know, there is no device other than windows file storage that can make any use of such cards.
If it is neither, then I don't know. I use M3 Real on my 8GB SDHC card and have never had any problems.