You don't have any other weird mods to your tablet installed do you?

Try putting a game disc in the drive. I did this so I could be sure eject was hit quickly enough.

Also, try viewing some of the videos online (not necessarily N810 specific) to see how it's done. This was how I learned that I shouldn't hit the hard power switch and then press eject but rather turn the switch on (so the PS3 had power but was off, not in standby), press the power button and then eject.