How would you go about asking for a job that you turned down not long ago?

So the long and short of it is that I am currently working as a contractor and basically do not get any benefits whatsoever. I have been waiting patiently for the company to bring me on as a full time employee as they have promised to do so, but it has been about 7–8 months now and it’s been delayed yet again because the parent company is doing bad (even though the contract I am on is doing great).

Well around December of last year, I was offered a position at another company, full time, better pay, vacation, the works. I think it’s a lateral move, but financially it would be a nice upgrade.

I approached my boss the day after it was offered to me and explained to him the job offer and the position I would be filling over there. He recommended that I stay with the company as he felt it would be in my best interest because I would be brought on board full time very soon (at a very similar rate as my other offer). Months later and I’m still not on board, and in fact it was promised that I would be brought on in April, but now its looking like July. To top that off, it is also quite a bit less $$ than I was led on to believe (though experience trumps $$ for me, so the money is just a nice perk)

Had I known that this would be the situation, I would have taken that other job in December because it’s something I thought I would be a great fit for and I have all the right experience with a bit of potential for some other technologies to learn.
I noticed that the job that I had been offered was just reposted (nearly 4 months later) and I am now re-considering my position on the situation. Is it too late to contact someone over there at the place that offered me a position in December and ask them if they might still be interested if I had changed my mind? I do not want to come across flaky or inconsistent, so I wonder if there is a good way to ask without seeming like either of those.

How would you flutherans out there approach the situation that I am in?