On my site I have a contact-form and my tests show that, depending on where you click, the search-panel gets focus so that pressing ENTER does not post the form, but initiate a search
Thats the ways its supposed to work, whichever form has the focus should post by the enter key. If the contact form has the focus the enter key works for it, if the blog post form has the focus the enter key works for it, if the search has focus the enter key works for it. Now really in asp.net there is only 1 form but the point remains the same as if there were multiple forms on the page, the one with the focus gets the enter key. This is the expected behavior.
In ASP.NET this is accomplished by wrapping a Panel around it and making a specific button the DefaultButton of the panel so that if the panel has focus the enter key triggers its default button.
I could have told you that redirect would not work because in IIS urls are not case sensitive so IIS sees no difference based on case. This really stems from the fact the the Windows file system is not case sensitive, whereas on linux file and folder names are case sensitive and therefore so are urls when hosted on linux with apache. The case sensitivity bug that was allowing the search form on the login page was in C# code.
The new release is coming soon but a preview release for MS SQL is available now and has this fix, you can download it now from Novell Forge.