Windows Vista Sleep has stopped working

[Clinton Bell]

Without me having knowingly changed any relevant settings, suddenly "Sleep"
no longer works on my Windows Vista.
Previously, when I selected Sleep from the switch-off options from the Start
menu, the system would shut down but when I re-started (by pressing the
physical "on" button on the computer), it would re-start quickly with all the
same programs and documents as before.
For some reason, this has stopped.
Does anyone know how to remedy this please?
Thnkas

 

[D Lirious]

The sleep mode is extremely unreliable and one of the many poorly
implemented features in Vista.
Microsoft is hyping Windows 7 as starting up so fast that sleep mode will be
irrelevant.
Alas WIn7 is but Vista SP3, another silk purse made from a sow's ear.
You are better off, as is the environment, shutting down your computer. I
doubt your time is so precious you can not afford to wait the extra minute
or so for the machine to reboot.