I don't think this contest depends on a serious problem with the C language. The 2008 winner (http://underhanded.xcott.com/?page_id=17) could have been written in any language.
Indeed, what impressed me about that entry was it was a fundamental error that is surprisingly subtle. It could have easily been implemented in Python in about the same number of lines.
That's true, I think that one is particularly impressive because for that reason. Nonetheless if you look at the majority of entries, the main techniques used are things like heavy wizardry with pointers, broken macros, and other preprocessor stuff, which, while admittedly not unique to C, are not so bad in most other languages.
