Howdy...
We are using the login action with a bit of a twist to login our DNN users. However we are having issues with locked or invalid username / password combos.
On the first failure, we can report back to the user correctly. On the second failure the form just goes blank.
First time:

Second Time:

I've posted my form code via Fiddle for ease of viewing:
http://dnndev.com/fiddle/fid/555
Is there something wrong with my approach? As far as I can tell the error messge is being returned correctly from the login attempt the second time.