What version are you using to do your SRs? If your answer is Emerald then you have your explanation. Emerald has a broken RNG that gives out the same numbers over and over again. I did somewhere in the range of 40,000 resets for shiny Treecko on Emerald before this was known. (I was even fully restarting my game every thousand, which was clearly not enough.)
Oh. >.> damn, no treecko for me. D: i have emerald, fire red and gold and silver, but i want treecko. lol.
Im getting both diamond and pearl soon. (as in this week) si ill be trying for more shinys. probably absol, Piplup and Mr Mime. * see yas!*