Just a few questions: Are you getting an error message when you try to save files to the SD card? Are you able to test an alternate SD card in your phone?
Here are a few steps to troubleshoot the SD:
If the device has issues recognizing or accessing a SD storage card, follow these steps:
Turn off the device.
Remove the SD card.
Insert the SD card again.
Turn on the device, and wait a minute for Android to read SD card.
For Android 1.5 /1/6, verify the storage card is not unmounted:
Tap SD Card & Phone Storage.
Check that the option to unmount the SD card is available.
View the available space on the storage card. When the SD card does not have enough Available space, you cannot store new pictures or other media on the phone. If there is less than 50 MB available, delete files on the storage card to free up space.
Test the SD card.
If problems continue, format the SD card.
Test the SD card again.
If problems continue, check that you are using the original SD card that came with the device. If not, then test the SD card in another Android phone to verify it works. Not using original SD and it fails in another device, the SD is defective. Please purchase another or use the one that came with the device.
Not using original SD and it works in another device, the SD is not compatible with your phone. Please purchase another or use the one that came with the device.
Hope this helps!