as you have figured it, this error comes with SSL encryption ... so, the "best" way to avoid any troubles is to disable it
So yes, that's the last resort way, but when you'll be bored trying to solve this problem, re-compile your nrpe with option "--disable-ssl" and problem solved
in the meantime, you can try to do a "ldd nrpe" (and also a "ldd check_nrpe" on the server, but that shouldn't be a problem if only one host is affected) to see if all the librairies are present.
You can also try to re-install openSSL on the client ...
but still, if all fails, just use "--disable-ssl"