Ok Robert, I have a couple solutions for you that may or may not work.
1. Try using Ethernet to connect to the router. If you achieve your normal speed using ethernet then you are most likely having a range problem.
2. Try manually forgetting the network from your computer. In your screenshot, it looks as if there is some type of error in the way your computer attempts to access the router. Forgetting the network and connecting again will force your computer to download those "settings" again.
3. Try running your computer directly into the modem (unplug the ethernet cable running into your router and connect your PC directly.) and see if you are achieving the speed you desire. If number 1 and 2 don't work and this does, You will need to purchase a new router.
4. Try using another device for the steps listed above. (If possible, use a friends PC to test it as the device has never connected to the network before.) If using another device fixes the problem you might be able to fix the problem by factory resetting your modem. This will wipe its database of all the devices that have connected to the network in the past.
5. Get a new router. Sometimes routers will just die. You may be more than able to fix your problem by buying a new router.
6. Check your cables. It's very simple and may save you a router purchase. Possibly buying new ethernet cables might help as well.
Number 5 will most likely solve your problem :)
Best of Luck,