For me personally I don't have this problem as I've had verbal diarrhoea for as long as I can remember.
I think the best advice mate, is for you just to treat it like you were talkin to a friend (within reason!). I mean, when was the last time you scripted a conversation with someone you were familiar with? The more natural the conversation goes, the more comfort you are going to build with a woman.

Another option, which I found VERY helpful when starting out, is to learn a few routines for when it goes quiet,, like the types Mystery talkes about in the MM.

Either way, you should just immerse youself in as many interractions as possible, and you will find that it is quite easy to keep conversation flowing, and that it is not at all a daunting prospect.

The more you do it the better you shall get!

Ritz