What is the highest class SD card that the D2 supports? I was looking at a class six, but I want to be sure that I won't have issues before I shell out the cash
I do not have a clue about what your are asking. Curious, I goggled "sd card class" and found this link. SD Speed Class - SD Association
I know it does not answer your question specifically abt D2 but it is informative. I'd suggest if you do not get any ans on here to call Verizon and ask.
I have a class 6 in mine and it works fine... however I don't know if it takes advantage of the extra speed. The original moto droid could use any class, but it only transferred at class 2 speeds even if you had a class 4 or 6... droid 2 might be that way as well, I have no idea.