Sandforce drives can enter a panic mode when a serious error has occurred. When a panic mode is instigated a log file is generated that provides a system snapshot of information that helps to debug the problem. The drive can accommodate 4 panic logs, after that the slots have to be cleared via a manufacturing-level format process.
If the LED light is permanently on (i.e. not blinking) it means that the drive is in panic mode and a panic log has been saved to the drive. (Some vendors do not follow the Sandforce reference design, so in some instances the LED will not follow this protocol).
If the drive is in a panic state data can only be recovered by a specialist, and even then it cannot be guaranteed. Drive Savers used to be an accredited Sandforce partner, not sure if they are now, but they are probably your best hope if you need to recover data.
As Brian mentioned, this is a rare occurrence, but a rather annoying one as you loose all data.