Are SDHC card different in any way other than their higher capacity?
R4 supports FAT32, so technically it should be possible to make "normal" sdcard that support higher capacity.
http://support.microsoft.com/kb/140365
See, even FAT16 can go to 16GB.
I have that problem too, it looks like the dstt sees white as transparent, i've seen the same thing happen when i opened some transparent pictures in Paint.
I've tried it. Changing DRAWINFO to 0 disables the top screen info, so there's not text at all, not the web-adres, the firmware version or the information about the file.