Short before Debian is freezing the upcoming release of a new version of nagios-plugins is scheduled for Wednesday. The good news is, that a recent version is available in unstable and testing. Upstream only fixed some check_ping issues, which are not included in nagios-plugins 1.4.16~pre1-1. There is also a package available through squeeze-backports.
If you are able to, please test the packages as soon as possible. If there are some quirks, these can be fixed in the next two days upstream.