Hmmm... After upgrading from 1.3.7.1 I am having this problem with my admin login. The user login works fine and all the data in mysql seems to have transfered over fine.

I checked, and my admin/login.php file is exactly the same as the one that 1.3.8 came with.

Any ideas?

Here's the link I am using:

http://birdingdepot.com

You need to add a "/demo" to that link to see my site in 1.3.8. I didn't want to add it because the next thing I know Google will index it!! :)