I have to agree with greenlydia - it would be best to talk to a pharmacist about the interactions.
Both Klonopin and Ativan are benzodiazepines, which, I'm sure, you know, but Klonopin is a longer acting one than Ativan, meaning it will take longer before it starts acting.
If I were you, I'd ask your psych doc as many questions as possible regarding meds. My mother suffers from bipolar and is on Lamictal, Paxil and Xanax as needed.