Does there exist a projective module over $k[x_1,...,x_n]$ which is not free?
Solution 1:
A CW answer to remove this from the unanswered list: All projective modules are free; this is the main result of this paper by Hyman Bass.
A CW answer to remove this from the unanswered list: All projective modules are free; this is the main result of this paper by Hyman Bass.