I acquired permanent residence status 3 years ago in Canada. My common law spouse sponsored me. I became eligible for citizenship of August 08 though I have not applied yet. In Sept, we separated due to an affair he was having. I went to a "free" legal clinic and received conflicting advice. One representative told me that I could lose my permanent residence since I did not legally marry this guy within a specified time and would not be ticking "single" when I applied for citizenship so I would not receive it and could be deported. Another representative said that as long as I maintained my legal status here (by staying in the country), then I cannot lose it. Please advise.

You legal status obtained based on relationship/marriage, it can be terminated as soon as the relationship ends or divorce in case you're married. If you apply for citizenship and get an approval while you're still together, you are safe. What the Rep told you is correct.