Nick wrote ..
I have a few butternut squash plants that are growing very well and
have produced a lot of flowers and small squashes. The problem is once
the squashes get to about 2-4inch long and the flower dies, the
squashes also die.

Can anyone tell me whats causing this and how I can prevent it.

They are not being pollinated, obviously not enough of the right insects
around your way so hand pollinate. Get a male flower, pull off the petals
and push it into the female flowers rubbing the male pollen of onto the
stigma.

--
Regards
Bob Hobden
17mls W. of London.UK