password recovery loop

I have a strange problem on my site. It doesn't happen to me when I use the recovery procedure from my test user accounts but I get tons of e-mails from members who say that when they submit the form, it tells them their e-mail address is invalid and returns them to the recovery form again. I have verified many many times that the e-mail address in their memberfiles is valid but they are still receiving that message.

any ideas why that is happening to people?

[filburt1]

Case-sensitivity? Extra leading or trailing spaces?

Or, best yet, are they entering in their actual e-mail addresses? Remember, users can be stupid

[drives fast]

true....I must keep reminding myself of that