Hello Tiago, thank you for your post.
The issue you describe seems to be related to integration. The only setting you can check, is on your laptop in device manager, double click on network adapters then on the Intel® adapter. In the advanced tab click on the “802.11n Mode” option, and make sure on the right it says “enabled”.
If this does not work then you may need to return the card to Dell as they would have sold you a card that has not been customized for this laptop. (Note that due to FCC and IEEE regulations these cards need to be customized by the laptop manufacturer to may sure that they are and stay compliant with the Radio regulations)
Thanks for your reply. That's the main problem. The option "802.11n Mode" is not present on the advanced dialog. Thus, I can't enable it. I wonder why all other wireless standards works just fine - A and G are both connecting normally, just the N option that's not showing.
So, as you're stating, this means that this card is not compatible with the notebook?
PS: How can I attach an image?
According to this product brief: http://www.intel.com.br/content/dam/www/public/us/en/documents/product-briefs/centrino-advanced-n-6230-brief.pdf, there are two versions of the Centrino 6230 wifi card - 62230ANHMW which supports 802.11a/b/g/n standards and the 62230AGHRU which supports only 802.11a/b/g standards.
The card I've received was the GHRU one, thus, the lack of the "802.11n Mode" option on the advanced settings.
I'm leaving this info here for future reference, in case anyone else have this same problem.
All the best,