>a. I need to talk to you about something.   
b. I need to talk about something to you.

Yes, option "a" seems to be more widespread. I guess "to you" is not really an object but is technically a "complement", a prepositional phrase, just like "about something". But semantically (judged by its meaning) it is an indirect object, and we tend to keep objects closer to the verb. Google Ngram [attests only option a][1]. 

The second sentence is understandable and probably grammatically correct, so I think both options are valid. But there could be cases where the use of this word order will result in ambiguity:

> a. I need to talk to you [about the things they did].  
b-1. I need to talk [about the things they did] to you.  
b-2. I need to talk about the things [they did to you]. 

With the word order changed, the majority of people will take the sentence to mean "they did something to you - let's talk about it". 

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Related:

* [A question on word order][2]  - ELL   
* The Cambridge Grammar of English Language - Ch 4, 4.3 "Ditransitive Clauses" - an explanation of why "to Sue" is technically a complement and not an indirect object in "I sent a copy to Sue"


  [1]: https://books.google.com/ngrams/graph?content=talk%20to%20you%20about%20something%2C%20talk%20about%20something%20to%20you&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Ctalk%20to%20you%20about%20something%3B%2Cc0
  [2]: http://ell.stackexchange.com/questions/3149/is-the-svompt-word-order-necessary-in-creating-a-sentence