What it probably means is that you did something -- cross a border, apply for a new PR card -- that gave CIC a reason to investigate whether you've maintained your PR status. Everyone who is a PR remains that way until their PR status is tested -- and then when it's tested, CIC will either confirm it (they are PRs) or decide it has been given up (if outside Canada, the person cannot enter; if inside Canada, they have 30 days to leave).
From what I understand, your PR is being tested right now, but CIC has not come to a decision -- so you are a PR. And, in my understanding, that means that you have the right to enter Canada, so long as you can prove your identity. Anyone can be hassled at the border, but there is no reason for you not to tell them the truth -- your PR status is being investigated, and you want to enter Canada. It might be a good idea to do it soon, since if they come to a decision revoking your PR, you might lose the right to enter.
However, it would also be a good idea to call CIC and make sure that you can, in fact, enter.