1. What is this all about? - This is, more or less nuetral. In my opinion, it's likely to indicate simple curiosity or wanting more information. Though one's tone of voice could change that. The word order, or the expression itself, is not enough to add meaning, as I hear it, however. By contrast, I feel that the word order in sentence number two is more likely to be less neutral, and therefore more likely to be expressive of something else other than the sentence's simple meaning. This would be heard in the speaker's tone of voice.
2. What is all this about? - Along with its simple meaning, this sentence, to me, sounds like it is more likely to indicate any of the following surprise, amazement, astonishment, confusion, dissatisfaction, displeasure, or annoyance. A speaker's tone of voice would indicate such things as well.
Both sentences may mean the same thing. However, the word order of the second one is more likely carry some additional pragamatic meaning, in my opinion.
Pragmatics - Answers.com: The study of language as it is used in a social context, including its effect on the interlocutors.
Consider one's specific choice of words when posting at an online forum or writing an email. Some of us are aware, for better or worse, that the words we use might carry something additional other than their simple meaning and what would appear to be their intended meaing. I think posters and email writers are aware of this and choose to be tactful or not tactful.
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