How to fix cannot repair wireless connection issue?

Hi,
I am using a Dell Inspiron Laptop but I am having an issue with my wireless connection. The issue is that, my wireless connection does not work properly. Meaning it works sporadically (sometimes it works; sometime it fails to do so).
I am using an Ethernet cable. My SSID shows connected and excellent and also my AT & T service includes an IP, which is constant. I have adopted different ways to overcome this problem but none of them helped me to handle this issue.
To solve this issue, I tried repairing my wireless connection but it ends with a message as, “The Window cannot finish repairing because the DNS cache cannot be cleared”. I also have tried few command prompts but no use and now I am hopeful to get some idea here to fix this issue. So, I need to know How to fix cannot repair wireless connection issue?
I need some help as early as possible because I really need to run wireless connection, on my laptop as early as it can be. Any help/suggestion is highly appreciated.
