I am typing at the moment from a DQ45CB with Core 2 Duo E8600 with 8GB DDR2-800MHz and a Corsair 430W Builder series PSU.
If you had previously set up amt on this board to wake up system on S3_S4_S5 power states this why you are getting the 5 seconds power up when you are connecting the power cord for first time after inactivity This behavior is normal for amt. I had also observed this behavior with my systems at work (HP DC7900 CMT) which have the same chip-set and AMT version 5.2. which is the case with DQ45CB with latest bios 0133.
My experience tells me that in order to have a proper working AMT system you might need a PSU at least 400w-450w.
fsofos, this problem nothing to do with PSU; in my desktop case I have same MB with 250W PSU and everything is working perfect, but you are definitely right about AMT problem.
1. Shut down your computer.
2. Move "Bios Configuration Jumper" to pins 2-3 and reboot.
3. Motherboard will automatically reboot to bios in configuration mode.
4. Now you will have extra item - AMT. Rest AMT.
5. Shut down the computer and move "Bios Configuration Jumper" back to pins 1-2 and reboot.
Now above problem should be solved