Sealant won't cure!

I used a standard Everbuild high-modulus general-purpose silicon sealant to fit a new door sill, it had the usual smell of acetic acid but it also had a curious lumpy texture, like porridge. Now 24 hours later it has not gone off, it's still as sticky as when I applied it. It is behaving more like the low-modulus stuff I have used for fitting double-glazed units in frames.

Anybody else come across this?

Sounds like you have used an old tube of sealant. also if I can add its the wrong sealant for sticking cills or trims you need low mod natural cure as what happens is the assertones between the plastic cause the trim etc to de laminate approx 12 to 18 months and you will be doing the job again,