For some reason, shadow copy isn't enabled by default in SBS 2008. Or rather - it's enabled on the C drive, but not other drives - where your data is likely located.
Of note - you enable shadow copies for a drive - not a share. So here's how you enable shadow copies for a drive.
Right click on the drive itself and Configure shadow copies. Select the drive and hit enable. This is a no-brainer to set up for clients, but typically, you won't do it until the first time you need it - which will be too late by then.