>Do you link Submit button with the Enter key? Because I remember I added a special code to make my Search button react on Enter.

Yes

>BTW, when I tried to log in to UT from my husband Win 8 laptop and IE 10, it was caught in the 'This operation requires a login' loop and I was not able to access UT.

For that, it would be best to have posted it in a separate thread. As for the issue, it seems the cookie is being rejected. You may want to take a look at this: http://www.levelextreme.com/ViewPageGenericCookieVerification.aspx