The system seems to enter standby (suspend) mode, but actually has not. This can be noted by the following symptoms:
The power button / LED are pulsing, indicating that the system is asleep.
The crescent moon indicator is lit, indicating that the system is asleep.
The display and backlight are off.
The fans are spinning, indicating that the system is awake.
The speaker and microphone mute buttons toggle if pressed, indicating that the system is awake.
The ThinkLight can be turned on and off, indicating that the system is awake.
The WLAN and WPAN indicators may be on (if they were on before the suspend operation was initiated they remain on), indicating that the system is awake.
There is no way to wake the system; in order to recover, the power button must be held down to turn the system off, then powered on again.
Since the system did not fully enter suspend mode, the battery will be drained quickly if the system is not connected to the AC power adapter.
Affected configurations
Any of the following ThinkPad systems running Windows 7 (32-bit, 64-bit), Vista (32-bit, 64-bit), XP may be affected by this symptom:
T410, T410i, T410s, T410si
T510, T510i
W510, W701, W701ds
X201, X201i, X201s, X201 Tablet
Solution
This issue is fixed in ME firmware update 6.1.32.1076 and is documented in the readme as: "(Fix) Fixed an issue that system hung intermittently when entering to suspend mode."