That doctronics picture of a breadboard is hard to read. Also they added a PNP transistor in there as an emitter follower for some reason.
Your circuit is more like 
http://upload.wikimedia.org/wikipedia/commons/thumb/1/19/555_Monostable.svg/275px-555_Monostable.svg.pngfrom Wiki, they have a nice write up on monostable mode. 555 timer IC - Wikipedia
We assume you dont have any missing grounds or power problem, something like that.
You add an inverter. Is it open collector? CMOS? Maybe try replacing it with just an open drain FET or transistor.
The other thing is the IO pin might do strange stuff very briefly during reset. We would hope it goes cleanly to hi-Z but maybe not. Do you have a scope? Or just try at pin 2 a 10K pull up, a 1k resistor to Arduino, and just keep adding capacitance to pin 2 