Php errors when I click on language switcher

I get the following errors when I click on language switcher on "my account" page. That does not happen on other pages of my store.

PHP Notice: Undefined index: email in /html/catalog/controller/account/login.php on line 121
2012-02-29 18:54:34 - PHP Notice: Undefined index: password in /html/catalog/controller/account/login.php on line 121
2012-02-29 18:54:34 - PHP Warning: Cannot modify header information - headers already sent by (output started at /html/index.php:100) in /html/system/engine/controller.php on line 28
2012-02-29 18:54:34 - PHP Warning: Cannot modify header information - headers already sent by (output started at /html/index.php:100) in /html/system/engine/controller.php on line 29



Anyone with the ideas of what might be wrong?

Thanks in advance!