I do hear the pump working and something "Unlatch" but thats about all and the Decklid does not go up. Could this be related to the problem you indicated?
There will be no mistake about identifying the pump running and the deck lid failing to lift, and there is one cause, the latch did not release quickly enough. You will see the lid trying (but failing) to lift. You might hear the unlatch sound, but if it is delayed the release mechanism will have jammed.
The design of the latch release is really very poor, the release occurs at the same instant as the deck lid starts to lift, so if for any reason it is slow then the likely effect is to jam the deck lid. The latch looks the same as earlier GM designs which use a lead screw and a motor to turn it, pulling the latch open. It happens quickly but not instantly, and I have found that with a low voltage, it happens too slowly to be released before the deck lid is pulling up strongly. Once the lid is lifting strongly, it jams the latch so it can't release (even though the latch motor is working fine). If you were to use the key in the bumper at that point, the deck lid will lift freely, because you can release the catch with the key.
If you press the 'trunk open' button on the remote at this point, it stops the pump.
If this is the cause of your problems, then for me the root cause was a poor battery.
If you have the headlights on when you switch the ignition off, how long does the odometer display for? (This assumes you have programmed the headlights to stay on after you switch the ignition off). The odometer should display for a good few seconds (around 15), but if your XLR is detecting battery problems the odometer will not display, flash briefly or go off very quickly.
If the odometer displays normally, then it doesn't prove you have a good battery, but it is a pointer that things are OK.
You didn't say if this problem arises with the N* running.