Try importing the footage again, I have a roscoby riser cam and it records to SD card as well, instead of capturing the footage to my normal file(on my external hard drive), I import it to "my videos" then when editing in pinnacle simply open that file and the footage will be ready for editing. Sounds to me like you may have a corrupt file and it is not loading properly, also pinnacle can be fickle sometimes and cause all kinds of lock ups and weird crap, it may be as simple as closing out of the program and rebooting.
Good luck!