Is Nokia N8 compatible with Nokia AC-10 microusb charger?

hmmm - I would vote for the DC power connector [round] charger as the DC connector can do 800milliamps, rather than just the 500mA that the Micro-USB does;    However that does not address your problem.    It almost sounds as if your phone thinks there is a device there [rather than a charger] and is trying to talk to it.  : for the phone to 'ignore' the USB charger as a 'Dumb' charger the USB charger must have the D+ and D- pins shorted : maybe there is a fault in the charger plug and the phone thinks the charger is a device ?

I am not quite sure that a Fake charger would be a problem ; shove 5volts onto V+ and 0volts onto V- then Short-together the D+ and D- in the USB and the phone will assume it is a Dumb-charger and just charge-away! 
- it simply won't care : there is nothing-much "genuine' inside a Nokia USB charger.

Perhaps the D+ and D- pins aren't shorted together? - this is part of the USB Dumb-charger specification : see Wikipedia - With No Short the phone will probably spend time trying to talk to a non-existant device down the wire.   
What does the phone do when plugged into a USB-port on a computer? - it that works then again suspect the charger.