I had a very similar problem some years ago with a wireless network card
i had only had it 3 days and i started getting loooooong response times, i kept doing speed checks via
Speed Test - dslreports.com and the 1 thing i noticed every time was a very high latency
i googel for a while to learn a little about latency only to find out that it is something that cannot be fixed with. i.e firmware - driver updates ect
[latency can also come from your isp, so best to check with another pc b4 you panic]
so i took the card out and got a refund and bought a new card of a different brand and hey presto no more problems
now not to say this is your problem but could be the answer
good look