I still have one solution that may solve your problem since it did for some people I know. Usually that degrade of speed can happen when a there is a conflict in the wireless networks detected by your PC.
Sometimes, your PC can automatically change to another connection with other settings, which in your case, could be another wireless access point your pc is trying to connect to, or maybe trying to connect to your router but with wrong settings.
This happens when your PC loses the signal from your router or has a weaker signal and try to get to another connection where it is stronger.
What I would suggest is if you check out the saved connections in control pannel ==> Network and Sharing Center
When you find the connections that your pc has already saved, right click and hit properties on each one of them to check out wether ur pc is allowed to automatically connect to them or not.
Hope this will help
For almost a year now I've had an ongoing issue with my wireless. Once or twice a day for an amount of time ranging from 15 minutes to a few hours the speed of my connection will degrade dramatically and in most cases web pages will time out while loading and online games(EVE online) will become unplayable.
A few facts about the problem:
-This seems to be isolated to one specific machine, as nobody else in the house has complained.
-I am using the standard issue Verizon router, the MI424 rev D and my service is Verizon FIOS.
-I have called Verizon and got the standard "Welll, er factory reset and buy more bandwidth" response.
-I have have performed a factory reset on said router, to no avail.
-It is not correlated with any game or program running. It happens no matter what is running, regardless of what is running in the background.
-I have already changed wireless connectors, with absolutely no change. The first one was a TEW-647 GA and I am currently using a Rosewill RNX-N300X
-This computer is in the opposite corner of the house from the router, but still gets a usable signal. My laptop and my tablet both connect perfectly without this issue in the same room.
My next step will probably be to replace the router. I use the Verizon one because of the on-demand TV service that apparently requires it.
Thanks in advance for any responses and any thoughts!