[TYPO3] Problem with Internet Explorer and acronym button

[Mat Colton]

Hi'y'all
using the RTE (Typo3 4.0.x series with RTE 1.3.9) and the Internet Explorer I 
have the problem, that the acronym button doesn't appear though it shows up 
perfectly in Firefox. I searched the web, but didn't find any information on 
my problem.

The HTMLAreaPluginList variable in the extension manager also 
contains "Acronym".

Parts of the TSconfig
****************************************************************
RTE.default {

hideButtons  = *
  showButtons (
    blockstylelabel,blockstyle,textstylelabel,textstyle,
    formatblock,formatblocklabel,cut,copy,paste,bold,
    italic,orderedlist,unorderedlist,acronym,link,
    subscript,superscript,image,line,toggleborders,
    findreplace,undo,redo,textindicator
  )
  toolbarOrder (
    bar,space,space,blockstylelabel,blockstyle,bar,space,
    formatblocklabel,formatblock,space,
    space,textindicator,linebreak,bold,italic,subscript,superscript,
    bar,space,orderedlist,unorderedlist,bar,space,acronym,link,
    image,insertcharacter,bar,space,
    cut,copy,paste,undo,redo,bar,space,findreplace
  )
}
****************************************************************

Any help is appreciated!
-- 
Bye,
Mat