IP Address becomes disabled!!!

Hello dears

I have found in RB1000 with RouterOS 4.2 a big problem.
After I set a new IP address over an ether interface, everything seems work fine, when I set any comment on it, this becomes unavailable!!! ping stops responding and I must to disable and enable the IP address for this to response again! It did not happened with earlier versions!

have you sent an email to Mikrotik support with the supout file attached? That might help identify why it’s locking up?
http://www.mikrotik.com/support.html