[TYPO3-english] version 4.2.6 problem

[Vahan Amirbekyan]

hi
I am having serious problems after upgrading to 4.2.6 from 4.2.2
After upgrade any FE user login session lasts until next click. FE users 
login but get kicked out with next click they make.
Troubleshooting shows that the reason is that fe_typo_user cookies value 
  is not equal to one saved in the fe_sessions table. I cannot find how 
it happens.
Rolling back to 4.2.2 does not help the situation. After rolling back to 
4.2.2 FE users cannot log in at all.

I need to mention that I am using "newloginbox" v3.0.1 that I was using 
with 4.2.2 for quite long time with no problem at all.

any lead would be much appreciated.
thank you
vahan