The fix for that error is documented in a MS support document.Error message when you run the ipconfig /flushdns command on a Windows XP-based computer: "Could not flush the DNS Resolver Cache: Function failed during execution."
Copied from the above link...To resolve this problem, follow these steps: 1.
Click Start, click Run, type services.msc, and then click OK. 2.
In the list of services, click DNS Client. 3.
Make sure that the Status column displays Started and that the Startup Type column displays Automatic. 4.
If the service is not set to Started or if the startup type for the DNS Client service is not set to Automatic, follow these steps:
a. Right-click DNS Client, and then click Properties.
b. In the DNS Client Properties dialog box, click the General tab, and then click Automatic in the Startup type list.
c. Click Start, click Apply, and then click OK.
Hope that helps,