how to change enblend parameter "--fine-mask"for PTBatcherGUI users

I'm using a precompiled version 2011.0.0 on win7 64bit
An error occured told me"Mask is entirely black, but white image was not identified as redundant"
According to panotools wiki
http://wiki.panotools.org/Hugin_FAQ#Enblend_error:_Mask_is_entirely_black.2C_but_white_image_was_not_identified_as_redundant
I should "use the additional enblend parameter "--fine-mask" to get rid of the error" but how am I going to do that when using PTBatcherGUI ? I think it's cause by taking 3 pictures at the same view with different exposure setting.
And the wikipage also mention about "This should be fixed in the latest enblend 4.0 release". So, is there anything I'm not doing right?

Thanks for your help.