>>>For a while, I get blank page (URL https://www.levelextreme.com/ViewPageGenericWorker.aspx) after the first login in Firefox. Subsequent login works.
>>
>>ACK
>>
>>But this is true since a lower number of hours, it worked for me 6 hours ago.
>
>I have no idea what you are saying.
>Keep in mind, that I'm not opening UT on new tab but it's open already on a tab that Firefox remembers from previous session.

ACK -> 0h06 -> (affirmative) acknowledgment

I see your behaviour and I do the same on my FF.

:)