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I looked through http://en.wikipedia.org/wiki/Category:Time_travel_television_series
but couldn't find anything fitting your description.
However, there's a film series listed on http://www.timetravelmovie.com/Time_Travel_Movie/TV_Series.html
that seems to match up: Josh Kirby... Time Warrior!
One of the movies is called Josh Kirby...Time Warrior: Trapped on Toyworld, as mentioned on that Yahoo question.
That is definitely it! Thanks so much, it's been bugging me for ages.
Sorry about that mistake - when it was broadcast over here, it was broadcast much like it was a TV series, so that's how I was remembering it. It's also going to be why I could never find it, because I was always looking for a TV series.
Thanks again.

Some TV show which on British TV I watched in the late 90s, early 2000s or thereabouts. However, it's possible it was an American import.
It was based around time travel, where some kid gets caught up in the misadventures of a collection of time travellers bouncing around time - one black guy in some time travel suit going up against a collection of misfits that includes some creature a lot like those old troll toys - I'm fairly sure it was called "Crystal" or something like that. It was also sensitive to something or other relevant to the plot - time energy or whatever other Mc Guffins.
I forget why they're travelling through time, but the kid tags along with the misfits trying to help them stop the black character. However, it later turns out that the leader of the misfits is the actual villain, and the black guy is the hero trying to stop him.
Real villain steals the timesuit, and then the kid has to team up with the black guy to try and stop him - but fortunately, the kid turns out to be some kind of Time Master, able to interfere with the flow of time once every 24 hours (which comes in useful when the misfits lose their time machine), but when he crashes into his own time line, he becomes depowered because only one of these time masters can exist simultaneously, and his younger self has taken precedence. (I believe they escape that by a girl with them sacrificing herself by removing the power source for some kind of time stabiliser she's wearing and falling out of time as a result.)
They eventually catch up with the villain, and defeat him by the kid ageing the stolen time suit tens of thousands of years, whereupon an earlier version of the hero turns up.
I think it all turns out to be just a dream, with all the different characters who were in the dream being people from his real life - and I'm fairly sure the girl turns up again wearing a "Crystal" necklace.
Sorry it's such a weird description, but it's years ago I saw it as a kid and I'm recalling only odd snippets of it.
I'm certain it's the same show as described here ( http://answers.yahoo.com/question/index?qid=20091001042142AAvaLZu
), but I am not completely confident about all the details that guy recalls.