Riobi Trimmer Loss Of Power...

[Chipchopper]

While using the trimmer with a hedge trimming attachment, I experienced a loss of power from the engine, after the blades came up against a thicker branch.
It starts ok but only runs at about 1/2 speed.
I've tried a different a attachment but it don't make any difference.
The offending branch turned out to be a loose stick that some idiot had poked into the hedge...dohh!
Any ideas of what the problem is and how to fix it, please.

[alavahalf]

Can you check the throttle cable hasn't slipped and reduced the revs needed to give you full power.