We had a problem with IE users not seeing the shoutbox depending on its content. Found out that it was a problem when using umlauts for the smileys codes. The smiley code will show up in the smileys alt-tag and block IEs XML parsing engine.
The general problem may be non UTF-8 characters in the shoutbox content. For example here the shout #975 contains an illegal character: GEN™
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