Mohinder determines that Hiro's body is rejecting his powers and he can't risk stopping time anymore.

He risked stopping for a moment, to turn and look.

Tell me now, because I don't want to risk stopping.

"I cannot even risk stopping in Tar Valon for help," Moiraine continued.

The only thing is then you'll run, when you stop and take your foot off the accelerator you risk stopping.

If the lymph nodes are clear, the physicians will then ponder the difficult decision of whether to risk stopping therapy.

Blade decided he'd do some first aid on her as soon as they could risk stopping.

Wherever she ran, she risked stopping a bullet.

He needed a paramedic with an oxygen bottle, but couldn't risk stopping resuscitation long enough to make the call.

And even if he decided not to risk stopping, in the event that word was out about him, he would come down somewhere and make it from there.