forms and multiple submit lead to a 404 page due to ?nocache=1

Hi,

I've built a form block on my website which allows people to subscribe to the newsletter.
There's no problem while I am authenticated but if i am an anonymous, boost adds ?nocache=1 to the url for each time I submit this form.
For example, if I submit the form once, the url looks like : www.mysite.com/?nocache=1
But if i submit it again, the url now looks like : www.mysite.com/%3Fnocache%3D1?nocache=1 and I am getting a 404 page not found error.

Is there any way to erase that ?nocache=1 or at least to be sure that one and just one will be added to my url ?

Cheers