You can imagine that the process of finding a fix for Vista Laptop Hibernate was not a straight road into to the horizon. A few things got messed up in the process. One of the intended fixes for Vista not waking up was the ACPI Lid driver that someone suggested replacing by a Windows Printer Driver in the device manager. The ACPI Lid driver then disappeared from the device manager. The laptop did not go to sleep anymore after closing the lid (Duh?). And, this was definitely not a solution for my laptop not waking up from hibernate either.
How to fix the "fix" - how to get your ACPI Lid driver back? I'll be brief. Someone posted a conversation chat with a customer support of Dell. Here is my little MOD which applies to ACPI Lid being replaced by a Windows Printer Driver (well, in my defense, desperate times require desperate measures, ha). First, you need to go into device manager and uninstall all ACPI drivers under "System". Then (and here's a rub) you need to find a Windows Printer Driver under Device Manager/System. There are two. You only need to uninstall the one who's description looks like ACPI Lid. That's it. You may need to reboot a couple of times and the ACPI drivers including ACPI Lid will reinstall themselves. In the process BOTH Windows Printer Drivers will mysteriously disappear from the Device Manager/System.
P.S.: I suggest changing the function of Lid Close to Hybernate, in your Vista power options because, as it turned out, Hibernate is more reliable than SLEEP. See previous blog post about the difference between hibernate and sleep after the fix.