gnumex cann't create.def files

I am unable to get gnumex to work. My current setup is:
gnumex 2.04
Windows 7 32bit
MinGW 20111118
Matlab R2011b

When I press "make options file" I get the following error:
 problem creating.def files: extracting symbols from lib-file failed

How to solve it?

Any help will be appreciated.

Thanks,
Hycere Hung