what's the difference between the two phrases?

Depends on what precedes and ends those statements.

Having no context makes this risky speculation, but I would say that "in company with" and "in the company of" probably mean about the same thing, ....well, no I take that back. They're basically saying that somebody is doing something with somebody else, but In company with" can mean that two people or groups are acting together for a common purpose, but they're not necessarily in the same place, e.g. Chrysler in company with Fiat are bringing the Fiat 500 to the US. "in the company of" is more likely to mean two people are physically together. "in the company with" is fairly strange, I'm not sure how it would be used, since it seems to mean something like two people are working for the same corporation.

thank you very much,nice man

thanks a lot, you are so serious

Note that the two phrases are subtly different, as Monterey Jack's post shows. One is "in the company of," but one is "in company with." There is no definite article in the second locution.

We saw here in the company of her schoolmates.

but

We saw her in company with her schoolmates.

thank you very much,I think I got all of you.

It could be used as "Sue was in the company of making rockets" or "Sue was in the company of family and friends."

oh dear the rocket just shot a foot off

That was not a foot; it was my big mouth! LOL

goodness you're limbre

http://en.wikipedia.org/wiki/Foot_in_Mouth_Award

Limbre in more ways than this one!

you mouth off?

You probably haven't been on a2k long enough to know!

i never miss a moment of your contributions

YOu really know how to waste your precious time!