what is the "+" sigh in the modules folder name?

I have a path on system called: '/lib/modules/2.6.37+/' It used to be called: '/lib/modules/2.6.37/' where did the plus come from? I'm asking because I have a /lib directory and the kernel sources for it. the problem is there is a closed source driver in the /lib directory and I want to compile a new kernel image, but can't re-compile the closed source modules. I'm guessing my new kernel isn't working because it's looking in the path with the + after being recompiled. thanks, Chris