Thanks for the reply. I tried WPA, WEP Auto and WPA2. None of those helped. In fact, as soon as I first tried WPA, my laptop's connection got much worse. It did not improve after trying the other security settings. Now, when I connect to my network, I get about 90 seconds of connectivity. After that, I am unable to access any websites. Running a speed test from Ookla sees a very low download speed (around 1.5) and no dectable upload speed. My ping is about 36. I have to start the speed test as soon as I connect to the network, before I am unable to acces any websites. By the time the test is finished, I can no longer connect to anything. Switching back to WPAPSKWPA2PSK (my original settings) has not helped, I am still unable to connect to any websites. To summarize, trying different security settings has made the situation go from frustrating to untenable.
I ran a speed test on my phone, using Wifi, while sitting in front of said laptop. It is getting around 15 down and 1.8 up, so I don't think it's any issue with the laptop's physical location in the house.
Any other suggestions? I am currently using 11b/g/n mixed mode, as anything else was making other devices in my home have a very slow connection.