i saw this issue as well.. i did skip all the v2 updates until 2.2.2 as i was migrating from 1.7.5 and had some issues with previous versions...
did you upgrade or are you on a fresh install? have you tried to go to version 2.2.2 and has this resolved the issue?
when i had this problem, i believe it was a permissions issue with the way the task/milestone was setup.. i would change the date and i would then not have the correct perms to view that task anymore, giving me a similar error.