Hi
In my old TomTom Go630, I use a' 16 GB SDCH Card, and it works smoothly with both, Internal memory and my External SDHC Card.
But ok I don't have to use the Internal memory, have exactly the same Navcore on my SDHC Card as in the Internal memory.
For those who have problems with SDHC Cards, try out other types of cards / brands ect ....
Regards.....