Bossing and crashes.

Maple randomly closes on me sometimes when I'm sitting in the middle of nowhere doing absolutely nothing.
I don't think there is any cause or way to prevent it.
I guess just make sure you have all the updated versions of DirectX, Microsoft .NET Framework, etc.

Obviously there's a cause, else you wouldn't dc. Whether it's due to not having the required elements to operate the software, bad code (a glitch) or a malicious attempt (hacking) is another issue, which would determine the preventability factor that you have control of as a player. Afk'ing in the middle of nowhere, you may have been the victim of the Evan map crash exploit that has currently been released to the public, which is the primary cause of most of the dc issues atm. It's such a pain setting up my shop permit being dc'd every other hour.

Kind of got of topic, but once you've determined the cause, you're able to take measures in order to prevent it from happening, whether that may be downloading and installing the required software or filing a bug report and hoping (need a lot of hope) that Nexon will acknowledge the problem, look into it, find the problematic code, and fix it.