Try updating with the latest files (tikipedia.tag.gz). That horizontal 1px line was fixed for sure, and probably the tab alignment as well, at least in IE6. Since updating to Firefox 3, I don't test as often in Firefox 2 so am not sure of the situation there, but will check.
Yes, I was trying to reduce the number of custom files in this version of the theme, but maybe went too far by just putting a login link at the page top. I'll look into having it reflect login status.