The webclient Uploadfile Methods Hangs

Question

The webclient Uploadfile method randomly Hangs. Can someone give me some assistance on the why the webclient UploadFile() function hangs.

WebClient client = new WebClient();
client.Credentials = CredentialCache.DefaultCredentials;
client.UploadFile(ipaddr, "POST", @"C:\Temp\ImageShow\White--Dot.png" ); //It hangs on this line randomly
client.Dispose();