In reply to mofonyx:
I have Bhutansa pair of Meindl Bhutans, and find they are superb scrambling and walking boots, which are very grippy on dry rock. I'd thoroughly recommend them for British 3-season mountaineering.
Vibram do lots of different grades of rubber, and the cheaper ones of these are a lot harder and less grippy, although I would have thought the Torontos would be ok.
Worn soles on boots are less grippy, but this depends how much you've used them - if the lugs are less than half what they were when new, they're probably less good. If you're new to scrambling, it's also possible that your technique isn't ideal, and this could be causing you to lose grip. The classic beginner error is leaning into the rock too much, instead of keeping your weight vertically above your feet. The BMC has some good videos on YouTube which show scrambling footwork, and heading out with someone experienced would also be useful.