Well, there are lots of explanations for that. First of all, Google recalculates everything each time you search. Add on top of that the fact that others are always competing and that variables like click rate affect rankings (though not much due to a history of abuse). Besides this each place you search from will be tailored (home vs. blackberry vs. office) in keeping with Google's attempt to personalize search for everyone (even if you're not logged on).

Keep fighting the good fight and eventually it should stabilize.

It can depend on your ISP as well. My bro in law live a mile up the road and when he does a search for one of my keywords, I appear on G page 2 and when I do it (logged out with cleared cache), I'm number 1. I know we also use different ISPs, he uses Virgin and I use BT.......don't worry, these things happen, just keep building backlinks and you'll be ok.

I know a lot of people will be logged into Gmail and have their search history enabled when they check rankings by hand. Make sure this isn't the case. Also, there can be slight in consistencies between DC's and Goooogle looooves new content. Just curious, did you publish it on more than one article directory?

I can also see same effects. Search engine result pages are very versatile until there is any page which have a very strong SEO value and a lot of backlinks.

It all depends on the cookies...dear..next time you try it clear your cookies in your browser and then search for your article...this will show you your exact rankings.