i was getting d/c from the router so i changed the admin access from the IP address i specified earlier to 0.0.0.0
and from that moment i cannot log on using winbox / ssh.
any suggestion on how can i gain access again.
Try with Mac based access, in winbox in field with IP address place a mac address from mikrotik interface that you want to access and try again …
just comes back saying wrong username and password.
when i tried web based login it came back saying :-
not allowed to login from this address (6)
its expecting the admin address to be 0.0.0.0
with mac server (enabled by default) you do not need any IP …just replace ip address to MAC address of your router and connect …
i dont have a time to make screenshots for you … too busy with some bugs in mikrotik BGP …they make me crazy over a two months ago …
Connect your router and your PC with lan cable.
Wait a while, and then click on the “three dots” located right to the field where you are supposed to enter the routers IP address.
This will bring up a list of MAC addresses that your PCs LAN card can see. It should show only one 
which is actually your routers MAC. Click on it, and the MAC will be copied to address field. Enter username and password, and you can log in for sure.
Or just connect a console cable to your router and your pc and log in that way
tried that, but could not log.
At last loaded another PC with routerOS and did MAC telnet. and it loged in.
somehow the router shuold have brought error, when i typed 0.0.0.0
but i learned one more thing.
Thanks for the help everyone !
manish,
have you tried to access router from specified subnet ?
sergejs,
mac-telnet does not need IP address assigned to your PC
Yes, jager 
you are correct.
IMHO, being unavailable to mac-telnet AND login via console cable is showing some hardware problem on the router.
manish, does the routers MAC address even shows up in the list in winbox?
And when you connect via console cable, does any readable text shows up on your screen? Ofcourse, set the correct serial port speed and parity…
allways follow to what are you setting by default there is /32 netmask 
and allways set up some backup user to get in anyways.