It is very unlikely that the wireless adapter will cause a slowdown in certain types of packets only; this should be specifically related to the network setup.
In case you have installed the Intel® Centrino Advanced-N 6235 wireless adapter in your laptop, as appears to be the case for the first post above, please note that you will need to contact the system manufacturer since this type of integration is not supported. Please refer to the following article.
Regulatory information regarding hardware installation or upgrade
http://www.intel.com/support/wireless/wlan/sb/cs-011644.htm
Please check the articles below for other recommended troubleshooting steps:
How do I improve my 802.11n wireless performance?
http://www.intel.com/support/wireless/wlan/4965agn/sb/CS-028449.htm
Access Point (AP) firmware updates may resolve wireless network issues
http://www.intel.com/support/wireless/wlan/sb/CS-006321.htm
If the issue persists after testing different drivers, updating the router’s firmware, verify the wireless/security settings and your wireless has never worked properly you may want to contact the computer manufacturer since it could be hardware related.