I had the same problem.
I fixed it by reinstalling Python2.6. The difference is that the first time (when virtualenv didn't work) I had installed it with the option "Only for this user", while the next time (when it worked) I reinstalled Python with the option "For all users".
I had the same problem.
I fixed it by reinstalling Python2.6. The difference is that the first time (when virtualenv didn't work) I had installed it with the option "Only for this user", while the next time (when it worked) I reinstalled Python with the option "For all users".