IME, standby leaves the power button flashing because the board is still powered to keep memory alive, so it shouldn't have appeared off
before. It would however be quiet because the voltage required is normally not enough to warrant use of cooling fans... or that area of the board is not powered.
Try starting in safe mode as Administrator, uninstalling all keyboard drivers, rebooting to CMOS/BIOS/Startup and looking through the areas, changing nothing but:
- On-board Devices - Enable onboard USB keyboard (if it is a USB keyboard)
- Power Settings - Wake on Keyboard (shut off wake on mouse if present and you have an optical [laser] mouse, as it is too sensitive and might not allow you to completely go into standby)
And taking notes on what you changed JIC.
Remember, don't change anything in this area unless you know
it is correct. If you accidentally change something, it is best to exit out without saving and start again with a reboot. Then when you're sure, F10 to save and exit, select Yes [Y and then Enter] and boot to normal windows.
Then when you reboot, drivers should install or you should be prompted for the driver disc
Very possible standby is not enabling completely or "Windows is hanging" on standby. Check Windows Updates for that or reenact the problem, note the time and check event viewer for errors. Event viewer is accessed by Administrative Tools or by typing eventvwr in the Run dialog box. Red Xs will be errors. Click on System or Application in the left column and search the right column for a red X (You'll see a lot of them most likely). Match the time the error occurred and then find the Event column on the toolbar, which will show the Product ID. Product ID is the ID of the component/program. Search google for the description you see when you double click (or right click > select properties) the Event in the right hand column.