When networks experience packet loss because of congestion or network errors, they can manifest as a frozen assessment. The assessment will seem to hang because it is either waiting for a response or sent a response that never made it out of the local network. We have noticed that large packets have a greater chance of failing on a congested or faulty network. This link is a simple page that will load 14 images of a boat ranging from 5 to 300kb in size. All images should load. If any one image does not load, your network is experiencing IP packet loss.
http://www.letsgolearn.com/ctg/file_test.html
A Comment on Wireless Networks.
Wireless networks generally have a much smaller absolute bandwidth than a wired network. So if your school or organization is using a wireless network for a lab of computers, it is very possible that you could be experiencing network congestion and thus IP packet loss. 2.4 gigahertz Cordless phones will absolutely interfere with most wireless networks because most wireless networks run at the same 2.4 gigahertz frequency.