I have samsung Galaxy spica and I tried to use class 6 sandisk sdhc with 8GB capacity, somehow, it wont work... on my spica it said that the card has been removed... completely not detected... and i have to mount the sd card from my handphone to detect it on the computer... I'm so confused.... please help.

What model Samsung camera? Is it compatible with SDHC cards or only with SD cards?

Throw it away and stop driving yourself crazy about it. They are cheap.

1 Insert your SanDisk 8GB memory card into a card reader connected to your computer.

2 Double-click "Macintosh HD" on your desktop.

3 Click on the "Applications" folder, then the "Utilities" folder.
4 Double-click "Disk Utility". Look on the left side to locate the drive that says "SanDisk.
5 Select the capacity of the drive on the left side of the window. The capacity will state "8GB" or "8,388,608 kilobytes." Click on the "Erase" tab to format the memory card. When you see "SanDisk" listed as the device's name, the capacity will be located above. You need to select the capacity and not the device.
6 Select the appropriate "Volume Format." Under the "Volume Format" button, select the format you wish to use. Select "Mac OS Extended" if the SanDisk 8GB will only be used on Macs, or "MS-DOS (FAT)" if you will share the card between a Mac and PC. Select "Erase" to complete the format of your SanDisk 8GB memory card.

If the 8Gb SD card works on your HD camera, then the problem is with your built in memory card of your computer. Most of the built in memory cards of the computer only supports up to 2Gb.
You can actually isolate it by trying to test an SD card lower than 8Gb to your computer.
Solution for this is to use external USB SD reader that supports high capacity SD card (SDHC) or contact the manufacturer of your computer and ask for firmware updates for the memory card reader. Hope this is clear and would help you.

The Digimax A7 may not be compatible with "High Capacity" SD Cards (SDHC). If this is the case you will need to locate an SD card that is 2GB or less in size as anything larger than this is a high capacity card.

SD card wikipedia page

The SD630 works with MMC and SD cards, 2GB or smaller. It does not work with higher-capacity SDHC cards.

Your SDHC card can be used in any camera that accepts SDHC cards.

Your reader has to be made for the ultra SDHC card.

There are no 8GB SD cards. Cards this size are SDHC (High Capacity). SD and SDHC cards fit the same slots, but many cameras won't work with the SDHC cards. SDHC is not backwards compatible.

There are no 8GB SD cards. Any card that size is an SDHC (High Capacity) card. SD and SDHC cards fit the same slots, but many cameras won't work with the SDHC cards. SDHC is not backwards compatible.

Any brand of SDHC card will be OK, if your camera can use SDHC at all. The difference between these cards is not the make so much as the class. The cheaper ones are class 2 (not very fast) while you pay more for class 6 (fast) or 8 (faster). The class should be specified, otherwise it's a slow one.

Your camera will accept a maximum SD card capacity of 1GB. It simply isn't capable of handling anything of a larger capacity and in particular is incompatible with the more technically advanced SDHC cards.

Your fix is to either replace your camera with a later model or to stick to using SD cards with a maximum 1GB capacity.