It appears (with an annoying 60% certainty) that MicroSD and MicroSDHC sizes overlap.
If MicroSD is using Fat32 and MicroSDHC is not using Fat32(??), this is significant.
So, it appears, both SD and SDHC comes in 4G, but different file systems.
This reference implies the above: SD Card: Information and Much More from Answers.com
....but doesn't state it outright. (I believe this is a copy off of Wikipedia)
This source supports the above statement, unless Samsung's PR
people were sloppy with distinguishing between the two formats: SAMSUNG Develops Mobile Phone Memory Card with Record Storage Capacity SAMSUNG
To add to the confusion, some BB-83xx's appear to report the capacity
correctly, even though they are not be able to use the full reported
blackberryFAQ.com just adds more confusion, stating a compatibility difference between 83xx models. [url=http://blackberryfaq.com/index.php/What_type_and_size_Media_Card_can_I_use_in_the_810 0_/_8300_/_8800%3F[/url]
The FAT32 thing isn't clarified either. Versions of fat32 have capacities ranging from 32GB to 8TB, (depending on the implementation), so fat32 all by itself is not a limiting factor.
Another reference says the incompatibility lies with memory addressing:
(sector addressing vs byte addressing) [url=http://en.wikipedia.org/wiki/Secure_Digital_card#SDHC[/url]
There's no shortage of opinion (guessing) on this though.....
Is there a way to get someone with some real authority on this to comment ?