Problem with disabled VT
Some Core Duo era ThinkPad models ship with Intel CPUs that implement VT-x for hardware-supported virtualization, but the capability is disabled by the BIOS. The only known solution is to flash a newer version of the affected ThinkPad's BIOS.
See this LKML thread for more information.
For some reason, VT-x is disabled by the BIOS on some ThinkPad models. Before you attempt a firmware update, you should check this article to confirm that your BIOS version has VT-x as a configurable option.
Available BIOS updates
In response to the missing and also disabled VT-x option in the BIOS, Lenovo has released several BIOS updates for the affected ThinkPads to fix the problem.
The Z61t, Z61e, Z61m, and the Z61p's BIOS has been updated to support VT-x as of 2.18. The X60, and the X60s's BIOS has been updated to support VT-x as of 2.06.