Due to a bug in OpenSSL Linux and Mac 64bit
Namecoin Classic (v0.3.80 and earlier) and Namecoin Core clients accept a wider range of cryptographic signature formats than other builds. This brings us into the dangerous situation of potentially forking the network.Miners
A majority of Namecoin hashrate is going to begin enforcing BIP66 circa Monday (2015-08-03). This means that all mining pools who don't want their blocks rejected after Monday MUST upgrade to Namecoin Core. Either 32-bit or 64-bit will be fine after BIP66 begins enforcement. (Before that point, we still recommend 32-bit). We apologize for the short notice here.Namecoin Core RepoLinux binaryInofficial Windows binaryUsers
Do not trust transactions until further notice. Do not purchase new names until further notice. If you have a name that is expiring very soon assume that transactions may be delayed unexpectedly, so renewing those names before the last minute is advisable.
If all goes well things will be mostly working again from Tuesday on (2015-08-04) but you will need to wait for six confirmations (more for important transactions).
(edited as per Biolizard89's suggestions)