'Invalid key' wp-login.php

Hi, when I use the ‘forgotten password’ or ‘register new user’ option in ‘wp-login’ l get an email with a link to change the password. Clicking the link results in the browser in an error ‘invalid key’. I investigated the problem and found that the link in the email is encapsulated in the symbols ‘ < link > ‘. When i copy the link without the leading and trailing ‘<>’ and paste it in the browser, it works fine. So my question is, were (wp-login.php ?) can i change the code so those symbols are not included in the email message.