Recently when I play WC3 on Battle.Net, I get a lot of the same crash. It says something about a fatal error, after my game is closed. It usually happens at the very start of a game, but sometimes just before I win. I'd say it happens roughly at a 3:5 ratio.

I'm not sure, but I think it might be a hack. I've checked the profiles of some of my opponents when the game crashes (have to read the error report, as "Last Replay" is not saved when it crashes like this) and they usually have unreal accounts, with, like, 100-0 stats, or similar.

Is it a hack or is my computer acting up? How can I stop this from happening?

Hello Starshaped

It sounds like the crash hack that is going around. Please report the issues using the following webform:
http://us.blizzard.com/support/article.xml?locale=en_US&tag=hacksform

Thanks for the update, yeah we are looking into the issue though I do not have an ETA for when it will be resolved.

I also forwarded the webpage issue along through my channels.