Hi Rick,
Looking for some advice on how to troubleshoot a problem with the USM password reset function. Of course, it works consistently in my dev and stage environments. Here's the pattern I've noticed.
When a user requests a reset, they are getting the user or password cannot be empty validation message. When I try it on their behalf, I also get this message. However, if I log in successfully, log out and then request a password reset, it works. I can then initiate as many password resets as I want. Maybe this has something to do with session? Anyway if you can think of some debugging tips I'd appreciate it.

The user or password empty message seems to indicate the data is not getting posted.
Use Fiddler to check what's going over the wire to make sure the data is actually getting sent. It seems odd this would be conditional - it should either work or not.
Until you are actually logged in Session should not have any bearing on password recovery or general non-logged in operations.
+++ Rick ---