ok. Solved
We found a conflict with CT Birthday Image Post in global_start hook.
This is a conflicting code:
PHP Code:
global $globaltemplates;
$globaltemplates = array_merge($globaltemplates, array('postbit_ct_birthday_box'));
It is not a vBET issue but we solved it.
We do not know what exactly is causing this error because vBet do not use this variable (global $globaltemplates;). it may error of php or vbulletin
Now everything works fine. Use Full File Cache For Guests is turn on!
If you ever do update this CT Birthday Image Post plugin you have to do these operations:
1. go to admincp -> Plugins & Products -> Plugin Manager
2. find CT Birthday Image Post
3. click on the CT birthday - Add To globaltemplates
Now you can edit options of this code. So:
4. find Execution Order field,
5. just edit from 5 to 6
6. click save button