Airport Internet Speed Slow

I have a Time Capsule 500GB Router. Recently it has a slow connection speed to the internet. The Las Vegas Speed Test ( http://test.lvcm.com) shows download speeds averaging 12.0 - 15.0 mps and upload speeds of 50-99 kps. If I connect my iMAC directly to the cable modem, the upload speeds improve to approximately 2.0 - 3.0 mps. Note that my IMAC is connected to the Time Capsule though an Ethernet cable (not wireless).

I was looking for similar posts on the web and found a gentleman who disabled his WINS (wireless service). I did the same to the Time Capsule and the upload speeds (hence the entire internet experience) returned to normal.

I restarted the wireless service using my prior SSID with WPA/WPA2 Personal security and speeds stay at normal. Other computers connected wireless accessing the internet enjoy similar high speeds. The lasts for some time until the internet upload speed slows down again. I can repeat the procedure (shut off the wireless, etc.) with the same result.
Has anyone seen this before?

CJM