Sometimes your SD card in your Android phone may become corrupted. This can cause may different issues, usually resulting in the PC sync being unable to perform properly or start at all. Follow the steps below to repair or reformat your SD card.

Format your SD card
Back up your data

Connect your Android device to your PC and mount it as a disk drive (i.e. mass storage mode).
On your PC, open Computer or My Computer and find your SD card/removable drive
In the Windows Control Panel, in Folder Options, in the view tab, make sure it is set to show hidden files/folders
Select Ctrl-A to select all files and folders in this drive and then right click and select Copy
Paste all of these files into a new folder you your Desktop
Format your SD card

Right click on your SD card drive in Computer or My Computer and select "Format..."
Leave all default settings and select "Start"
When the format completes, copy all of your data (previously backed up above) back on to your SD card
Perform a chkdsk
Connect your Android device to your PC and mount it as a disk drive (i.e. mass storage mode).
On your PC, open My Computer and take note of the drive letter that's assigned to your Android device's sd card.
On your PC, click on Start -> All Programs -> Accessories -> Command Prompt.
Enter the following command: chkdsk [sd card drive letter]: /r