I have a 16 GB SDHC formatted to FAT32. I am using OSX 10.5.7 and DellEFI 1.2a5 with Melkor's Touchpad driver v17.
If I try and do some more intensive writes to the SDHC card in the internal slot, then I can almost guarantee Finder will hang (whirly wheel).
For example, I have a 2.85GB Ubuntu VirtualBox vdi image and copying that to the SDHC hung 2.1GB in. Doing the same thing using the same SHDC card in my USB SDHC card reader works fine, so it looks like a driver problem with the internal SDHC reader.
So is there a more recent version of the SDHC reader driver (ktext) that I should try?