This sounds like a network problem for the customer. You'd have to diagnose the network problems on the computer or the LAN for the customer.
Update not downloading
On one of our client machines, the update stops mid download, sometimes it's 4Mb, sometimes 30MB, max it got to was 115MB, then it just stops downloading, after a long enough wait there is an error message.
I turned off AV, same problem.
I manually installed the files, and ran wyUpdate again, which worked when the update was only a 4MB patch to download.
One thing I noticed on his computer, if a bat file was set to be executed (hidden) by wyUpdate, the cmd window was showing and the user was asked if he wanted to run the file...
Normally an elevation occurs (Win7), but this did not happen. The user did have privileges to edit Program Files without elevation...
Do you have any ideas why the download would stop randomly? It's only one out of 100's of machines, I'm not too bothered but would like to hear if you have any ideas on the configuration of his system.