@patlecat:
The problem is in your compiler settings in Code::Blocks, apparently. The (correct) default is for it to use mingw32-g++.exe to link your program: the g++ driver ensures that necessary libraries for C++ programs are linked in, whereas the gcc driver requires them to be linked explicitly. Since I don't know what other changes you've made, I would like it best if you could completely reset your compiler settings in C::B. If that's not an option for you, at least make sure that, as mentioned above, mingw32-g++.exe is being used rather than mingw32-gcc-4.2.0.exe.
@snija:
Thanks for the info! I will probably attempt a libgomp build tomorrow, along with GFortran and GCJ. If it goes smoothly, I'll find a way of making it available.
@heromyth:
The issue that you mentioned is certainly present in many other unofficial builds, but I've taken pains to guarantee that it is not the case for mine! (If it were the case, no one would be able to use this build, because it was built in "/extra/crossgcc" a Linux environment!) You can feel free to install it anywhere, and call it from anywhere.