Yes, it seemed like your load was exceeding the default (10.0) value, and npcd was not running. Depending on the number of CPUs that you have, you can increase the threshold in the npcd.cfg (x number of CPUs):
single core -> load_threshold = 10.0
dual core -> load_threshold = 20.0
quad core -> load_threshold = 40.0
You can also increase the timeout value in the "process_perfdata.cfg", let's say from 5 to 10.
Restart npcd:
Depending on your server's resources, npcd can eventually "catch up" with processing these files. You need to watch the load on the server. The other option would be to delete all of these files (see my previous post).