Comment 64 for bug 610915

I am having this problem as well. I had both "myUser" and "myuser" saved in Firefox. My site actually has the username "myuser", but the other one was saved by mistake. When I login with user name "myuser", Firefox automatically changed the username to the saved username "myUser" in spite of having both saved!

This happens when I use tab to go to the password field (which most of us do I guess). When I use the mouse to manually go to the password field, it seems to work fine. Then I have to manually delete the entry "myUser" from Saved passwords and it works without issue. The browser cannot automatically assume the username since many sites let you create case sensitive login names.