If the replacement caps were bad or wired polarity reversed, both power on and power off circuits would be behaving badly, and if the system was jumpstarted then turning it off could be a problem. Not to accuse you of anything, but this might be a good time to remind readers that on aluminum electrolytics, the bar mark is on the negative, and just to be difficult, on tantalums the bar mark is usually on the positive terminal. If the old caps farted on the circuit board and changed some connections, the new circuit could be trying to establish a warp field to an alternate universe. A very thorough visual inspection in good light might reveal something. Verify with a voltmeter that you do indeed have good +5V continuous.

Take a look at the startup schematic for ideas on what next to check-

http://home.earthlink.net/~gamba2/images/macIIcisch.GIF but keep in mind that capacitor goo may have wired something else...