Yes.
PingPlotter sends and receives network traffic, and anything blocking this traffic will impact the ability of PingPlotter to work.
We have numerous articles in our knowledge base about firewalls blocking PingPlotter, including (but not limited to) these:
http://www.nessoft.com/kb/41http://www.nessoft.com/kb/27http://www.nessoft.com/kb/29If you're having specific symptoms, and you'd like to check and see if your firewall could possibly be causing this, please let us know what you're seeing and we'll be glad to comment.
- Pete