merge from smf 2.x to mybb 1.8 accounts problem

[PaBLo__]

hello everyone , so i have decided to move to mybb because it's more secure and awesome 

i have imported everything from smf except avatars because i lost them ( that's not a problem i guess ) 
my problem is sometimes when i logout and log back in i find myself using different member account , i though maybe happens because of converting password plugin and i removed it , but i still have the problem 

some regular users login with admin accounts please i need a fix for this asap
for example my username is pablo_ when i logout and login again ( SOMTIMES ) i find myself using ticket account witch is another account

[Jones H]

Does this also happen with newly created accounts or only with merged ones?

[PaBLo__]

Does this also happen with newly created accounts or only with merged ones?

thank you jones for replying , after making some search i found it's a cookies problem and i fixed the solution by removing settings.php from /inc