I know this news is gonna suck, but you probably have a virus. I had the same problem, and after 2, hour long phone calls to tech support, they decided that I probably had a virus. So, I got a checker and sure enough, 1208 of my files were infected, including Game.exe for Diablo2.
So, here's what you should do:
go to http://www.centralcommand.com and click on products at the top of the screen. Download the trial version of AntiVirus eXpert Pro and use it to scan your entire computer (memory, boot sector, ports, the whole deal) This will tell you what virus you have (assuming you have one). Make sure that in the actions tab of AntiVirus eXpert that you click on disinfect automatically.
This should clean it all up for ya, unless you have the Win32.Cabanas.B virus, then you have to wipe the drive(s) and start from scratch.
OH... make sure you turn off the murphy protector thing that installs itself when you install AntiVirus eXpert. Murphy is a pain and has caused my system to crash several times (mostly while installing).
For whatever reason (probably to prevent hacking) the D2 executable is one of the most finiky I have every come accross. If the size is different by even a byte, it will not patch or run correctly.
I hope this helps. If you have any more questions you can reach my at
[email protected], or on AIM as SwimCaptain1
Good Luck
Lans