Developer version is 28 and Stable is 27.
Yesterday this link http://www.opera.com/pl/computer/beta pointed to 27.0.1689.44. I've checked web installer, offline installer (where file name contains full version specyfication) and Opera/about checking version.
Today my opera is upgraded to 28.0.1750.15.
Besides I've checked stable version 27.0.1689.66. On both: dev and stable problem does not exists any more.