Taking pictures with memory card

A friend of mine has recently purchased a vivicam 3660. The camera takes pictures with the internal memory, but not when you insert the SD card. It recognises the card and tells you how many pictures are left to take on it, but when you press the button to take the picture nothing happens. A small blue symbol appears but the picture does not take. The user manual is useless and tells you nothing about what the symbol might mean. The SD card is not locked - I've tried it with the switch in both positions. I know someone else has posted with a similar problem, but she didn't get a reply. If anyone could help I'd be really grateful,
Thanks
Hetty