No cold water in the bathroom sink?

I've had no cold water in the bathroom sink upstairs for the last 2 days. I have hot water (not a mixer tap).
Toilet flushes fine and shower releases cold and hot water (through mixer tap) fine.
Water in the kitchen is fine.
I have a combi boiler.
I have recently noticed what sounds like pipe(s) shaking initially when you turn the water on & off. (dont know which pipe(s)). Cant say I've noticed it since we've been without cold water upstairs - it could be completely un-related - any ideas?

Steve
January 2012