Software Update and FTP issues

[zeroatma]

My wife has a MacBook Core2Duo, 4GB RAM, running 10.5.6. Whenever she tries to use Software Update, she gets the message:

"Software Update can’t find the update server. Make sure you’re connected to the Internet, then try again. Software Update can't check for updates because of a network problem."

This in and of itself wouldn't be a big problem, but simultaneously, she started experiencing problems using FTP to connect to her website server and her iSync/MobileMe disk.

We're both on the same wireless network, with identical Airport settings (I have an equivalent black MacBook as her white one). We can connect to her server using the same FTP program on my computer, as well as Software Update, with no problems. I can't find any difference in our settings, but something must be wrong.

Any advice? Formatting and reinstalling OS X is a LAST resort, but she needs to be able to connect to her servers for her work.

[MisterMe]

Check your wife's proxy settings.

[zeroatma]

Looks like it's helping us narrow the problem down. When I go into her proxy settings, it's set to "Using a PAC File". I switch it to manual, click OK then Apply, and when I go back into proxy settings, it's back to PAC File. By contrast, my proxy settings are always set to manual.
Perhaps this is part of the problem...

[zeroatma]

it looks like this is NOT actually related. I made sure all of her proxy settings are the same as mine (got it stay Manual), as are all the other Advanced network settings, and still no improvement.