To continue from Nicholaz's answer this reveals some wake events in the event log that I missed out, since they were not errors:
To find out what caused your computer to wake from sleep, do the following:
Open Event Viewer by clicking the Start button , clicking Control Panel, clicking System and Maintenance, clicking Administrative Tools, and then double-clicking Event Viewer. If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
Expand Windows Logs, and then click System.
In the Actions pane, click Filter Current Log.
In the Filter Current Log dialog box, in the Logged list, select the time range.
In the Event sources list, select Power-Troubleshooter, and then click OK.
In Event Viewer, in the System pane, select the date and time for the event that you want to view.
On the General tab, view the Wake Source for the event.
After inspecting the filtered results, I see plenty of messages like so:
The system has resumed from sleep.
Sleep Time: 2010-02-24T23:42:44.283678200Z
Wake Time: 2010-02-24T23:43:10.233041900Z
Wake Source: Device -USB Root Hub
However, I've also spotted this rather annoying "unknown source" variant:
The system has resumed from sleep.
Sleep Time: 2010-02-20T22:41:30.687040200Z
Wake Time: 2010-02-21T10:07:54.488171000Z
Wake Source: Unknown
I will update my answer if the solution is disallowing this device to wake the computer.
Update:
I have resolved my issue!
Turns out that the "USB Root Hub" source is a little misleading; it was actually both my keyboard and mouse that were waking up my computer (without being touched/pressed). The solution was to uncheck "Allow this device to wake up the computer" on both the mouse and keyboard devices (selecting them independently does not resolve the issue).
Perhaps updating my mouse/keyboard drivers will fully resolve the issue.
We had a similar issue with our T410's. On our problem, things would appear again, but it could be 20 minutes later. We found that if you install the Lenovo Power Manager (and its driver) it seems to go away.
also, you might want to try booting with the embedded Intel card as the video device, (set it in the BIOS) just to double check its not a hardware issue.
Best Answer
The c:\hiberfile.sys file is not used for sleep mode, only hibernation. So corruption of that file is definitely not the issue here.
This is almost certainly a driver issue. It looks like your graphics card is not correctly handling going from S3 back to S0 (sleep back to fully powered on).
1) Try updating your graphics card driver
2) Try rolling back your graphics card driver to a previous known good version
3) Failing that driver rollback, try using System Restore to go back to a system state prior to the manifestation of your problem.