I have an Acer digital camera CR-8530. When I put a new SD card in it it gives me "card error" message. Why nd what can I do?

The camera uses SD cards. I assume your new card is 8GB, not 8MB as you stated. If this is the case, it's an SDHC card. While it fits into the slot, it is electronically incompatible and will not work in the SD-only camera. You need to use SD cards, 2GB and smaller.
You may download a copy of the manual here.

SD cards have a small micro switch on the side check to make sure your's is open/on.

First make sure you transferred all important pictures from your SD card to your computer.

Then format the SD card "using your camera". Don't format it using your computer.

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well as long as it works when u put the sd card in then its all good right?
also

1. DCF Full Error error message. The DCF error message with your Samsung camera nearly always occurs when you're using a memory card that was formatted with a different camera, and the file format structure is not compatible with your Samsung camera. You'll have to format the card with the Samsung camera. However, make sure you download any photos to your computer first.
   

The problem is that your camera will only read SD cards, not SDHC cards. After you damaged the SD card that you've been using for years, you bought a replacement, not noticing that it was SDHC. The new cards don't work, not because they or the camera are broken, but because they're not compatible.

Cards up to 2Gb are generally SD. Cards over 8Gb have to be SDHC. 4Gb cards can be either SD or SDHC, but are almost always SDHC because they're cheaper. (I would avoid the rare, expensive, and problematic 4Gb SD cards.)

Your solution is to go find a 2Gb card, and be extra sure that it doesn't say "SDHC" on it. (If it does, it probably means that they made a 4Gb card, but there were some error locations and so they disabled half of it and packaged it as a cheap-brand 2Gb.)

The lever on your SD card might be turned the wrong way so the SD card is reading protective.
Please turn the lever and try again.

The SD card might not be supported by the model: Your camera Memory card support is SD/MMC up to 2 Gigabyte and SDHC up to 8 Gigabyte

The SD card might not be faulty, try another card, since the camera could give you a message like the one you're experiencing.
Try with a different SD card that is supported by the camera.

I'm guessing you bought a new 4GB SDHC card. Although it looks exactly the same as a standard SD card, the format the card uses is very different. Unfortunately your camera was designed before the SDHC format came out. Sorry, but a SDHC card will not work with your camera.

You'll need to use standard SD cards (usually those 2GB or less). But if you really want to use a 4GB card, do a Google search for 4GB SD "non HC", with the non HC in quotes. Believe Transcend makes one.

I'm guessing that you bought a new 4GB SDHC card. Although it looks exactly the same as a standard SD card, the format the card uses is very different. Unfortunately your camera was designed before the SDHC format came out. Sorry, but a SDHC card will not work with your camera.

You'll need to use standard SD cards (usually those 2GB or less). But if you really want to use a 4GB card, do a Google search for 4GB SD "non HC", with the non HC in quotes. Believe Transcend makes one.

Remove SD card, then whilst card is removed, delete all pictures that may still be stored in cameras 'internal' memory (usually just a few) then replace SD card. Should be unlocked now?.

i want to place a 2gb memory card in the acer cr5130 but always i have the message card error .. i have tried several cards but always the some... please advice