Here is the CSS rule for your TinyMCE theme / style file that works for me:
.sclSkin table.mceToolbar, .sclSkin tr.mceFirst .mceToolbar tr td, .sclSkin tr.mceLast .mceToolbar tr td { float: left; }
Be sure to replace .sclSkin above with the name / identifier of your theme / skin;
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