I'm using a custom theme that's been working for six months. Yesterday I tried to edit my "sidebar.php" to add a simple mailto link. Just some plain html, nothing special.
I uploaded the file with FileZilla, as I always have. Then, the sidebar.php breaks my whole page layout. So I switch to Twenty eleven theme, uninstall my theme, and try re installing it (using Word Press' ZIP install). The dashboard just hangs after putting in my ftp info. Sometimes I get to the "unpacking package" stage, then it hangs.
I tried using many downloaded themes, same results.
It doesn't save my changes when I modify a theme using the dashboard editor either.
So I can't modify or install ANY themes any more.