I do not think there are any restrictions - I use a 2GB Hoodman card and haven't had any problems -- I would suggest contacting the company I bought it from to double check --
http://www.upcr10l.com/ -- tell them I referred you and ask them -- if you get an answer please post it here -- I will tell you that I have used it for about 5 different events with no challenges and only wonderful results!
happy shooting