First, if you haven't already done so, go into the camera menu and tryformatting the card (most cameras do it automatically, but always agood idea to make sure by doing it manually with a new card). If this doesn't work, then keep reading.
From what information I can find on your model it appears to be budget model which is based upon older technology (from around 2004/2005). That doesn't mean it's a bad camera; it's just a very sensible way for low cost brands to keep costs down using reliable and tested technology with low cost production licences.
Officially it's fully sd card compliant, but definitely not sdhc compliant. Your memory card is an sd card though so that's not the problem, but it is a higher performance example which increases the chances of older tech cameras throwing their toys out of the pram...
What I think is happening is that when the original sd technical standards were created there were no cards available above 500Mb (0.5Gb), so although the standard allowed for 2Gb cards there were none to actually test the cameras with. Many cameras of the time were therefore incompatible with anything above 1Gb and a few could only cope with 500Mb reliably. Higher capacity sdhc cards were then coming into use and newer cameras were built with the hardware to use them, so further development and firmware updates for sd got left behind.
I suggest that you try a 1Gb card instead, or even a 500Mb example if you can still get one, and as vanilla a version a possible (i.e. don't pay extra for ultra this or high speed that but it's still a good idea to stick to established brand names). Your camera is only 5 megapixels so even the smaller capacity version will still hold hundreds of images if set to record standard quality
jpegs and about 200 if set to record high quality
jpegs (always use the latter if possible).
If this doesn't solve your problem then the camera is probably faulty and should be returned for exchange or refund. With all due respect, you can get established brand name models for only a tiny bit more so personally I'd err on the side of caution and get a refund if possible. Again, I'm not claiming that Yakumo are bad, but you'll have trouble finding anyone that knows much about cameras who's heard of them so there will certainly be a smaller knowledge base available.
I sincerely hope that you fix this problem soon and that you have found my reply to be informative and useful. Please take a moment to rate my answer in response.