|The managerial brush-off is never a good sign. You are approaching your manager with a serious question, and he is responding with platitudes.|
However, your first step is to look at yourself to see if you may be the source of the problem. For example, have you developed the skills necessary to complete the assignments that you seek? Or, could it be that the assignments are challenging enough, but you have been through the drill so many times that you are bored with them?
If you are truly the recipient of the less-than-desirable assignments, and you honestly believe that you have the skills and abilities to carry out more challenging work, you should meet again with your manager. Rather than expressing dissatisfaction with a particular assignment, ask your manager what you specifically need to do to receive a different type of assignment. The next step is to follow his recommendations and let him know that you are doing so.
If he continues to hand you marginal assignments and platitudes, perhaps it is time to seek out a work situation that truly matches assignments with your skills.