PHP error when logging in

Hi everyone.

My website http://Quintex-finance.com works fine, but when I login I get this error message :

***
Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, ‘last_user_login’ was given in /home/traderje/public_html/wp-includes/plugin.php on line 395

Warning: Cannot modify header information – headers already sent by (output started at /home/traderje/public_html/wp-includes/plugin.php:395) in /home/traderje/public_html/wp-includes/pluggable.php on line 890
***

The URL when the error message shows up is http://quintex-finance.com/wp-login.php
Now If I got back to my home page. The log in did take effect.
Dont really know what to think of that, as it only happened since I changed web host (domain remained the same).

Would appreciate any help, and remain available if you need more info.
Regards.
Jean