We had a problem today with tinymce on Drupal 6, with a large number of buttons enabled the width of the tinymce button area just kept on growing - not pretty
Adding the following CSS to our Drupal 6 theme solved the tinymce button problem
.defaultSkin table.mceToolbar,
.defaultSkin tr.mceFirst .mceToolbar tr td,
.defaultSkin tr.mceLast .mceToolbar tr td {
float:left;
}
.defaultSkin table.mceToolbar{
float:left;
}