We have replaced the 4.6.17 release with a 4.6.18 release. This addresses some 4.6.17 regressions that notably affect CiviVolunteer and the estimating groups count on the mailing screen. There was also a pdf creation related error. The issues are to do with 4.6.17 security backports from 4.7 that missed something out.
If you have not yet gotten the security fixes in 4.6.17 you should choose 4.6.18.