We had the similar problem for a long time. We went through checking the network, router, Vista issues and all for about a month, changed the router, had our IT guy spend about 4 hours. Finally was able to fix it. The problem was Norton. Amazing chart doesn't work with Norton. If you have Norton, definitely that is the problem. Get rid of it. You have to remove it completely, go to Symantec website and download Norton removal tool to remove it from the computer.
Divak
