A Bug in WordPress v 2.5.1, originally uploaded by asim.zeeshan.
Excerpts from PHPCommunity
I discovered a BUG in WordPress Version 2.5.1, the forgot password sends you an email with the “key” that is supposed to generate a new email but the “key” itself contains characters like “&” which appends to the URL like query string and wordpress gives an error that the “key” is invalid.