Getting Error after upgrading

[friendlymela]

I have recently upgrade VB.4.2.1 to VB 4.2.2 patch one on my forum www.friendlymela.com now i am getting following error and i cannot access of admincp



Warning: Only variables should be assigned by reference in ..../includes/class_bootstrap.php(909) : eval()'d code on line 4

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at ..../includes/class_core.php:5755) in ..../includes/facebook/facebook.php on line 49
Unable to add cookies, header already sent.
File: /home/r/public_html/includes/class_core.php
Line: 5755

[ForceHSS]

Disable all plugins then enable each one to find the problem one might just need an update to it
Or
There are few things which can produce this warning :
If you are using cookie-based sessions, you must call session_start()before anything is outputted to the browser.
Remember that header() must be called before any actual output is sent, Either by normal HTML tags, blank lines in a file, or from PHP. It is a very common error to read code with include(), or require(), functions, or Another file access function, and have spaces or empty lines that are output before header() is called. The same problem exists when using a single PHP/HTML file. - Or maybe the problem is about the corrupted characters before <?php . Those appear when you changed encoding ANSII to UTF-8. Edit your configuration.php with a HEX editor or re-encode it with Notepad++ and select "Encode in UTF-8 without BOM".
http://bytes.com/topic/php/insights/876324-php-common-newbie-pitfalls-1-headers-already-sent

[friendlymela]

Disable all plugins then enable each one to find the problem one might just need an update to it
Or
There are few things which can produce this warning :
If you are using cookie-based sessions, you must call session_start()before anything is outputted to the browser.
Remember that header() must be called before any actual output is sent, Either by normal HTML tags, blank lines in a file, or from PHP. It is a very common error to read code with include(), or require(), functions, or Another file access function, and have spaces or empty lines that are output before header() is called. The same problem exists when using a single PHP/HTML file. - Or maybe the problem is about the corrupted characters before <?php . Those appear when you changed encoding ANSII to UTF-8. Edit your configuration.php with a HEX editor or re-encode it with Notepad++ and select "Encode in UTF-8 without BOM".
http://bytes.com/topic/php/insights/876324-php-common-newbie-pitfalls-1-headers-already-sent
how i disable all plugin i cannot access of admincp because of this error

[ForceHSS]

To temporarily disable the plugin system, edit includes/config.php and add this line right under <?php

define('DISABLE_HOOKS', true);

[friendlymela]

To temporarily disable the plugin system, edit includes/config.php and add this line right under <?php

define('DISABLE_HOOKS', true);

yap i have disable all plugin from config.php now i need to disable plugin one by one?

[bzcomputers]

yap i have disable all plugin from config.php now i need to disable plugin one by one?

No, just disable all your add-on mods. Then re-enable each mod/product one-by-one to see which one is causing the conflict. Then report the issue on that mods page, my guess is you'll find others have had the same issues with it and there may even be a fix posted.