Help needed - could it be my chains? Slipped a tooth?

[lairy_1 0]

Hi all. Need a bit of help with a problem my vr6 has got. Over the past month, I've heard a very slight 'scraping' coming from the chains at low revs, so was planning on doing them when I'm off work in august. But yesterday, the car turned over for a long time and refused to start. It did start on the second try, but made a strange noise like compressed air escaping.

A friend of mine suggested that it could be that the chain has slipped a tooth, so the timing is out. Does that sound likely? In that case, I assume it's not safe to drive until the chain guides/ tensioners are changed?

Is there anything else it could be?  

Matt