Tried Disc Defragmentation? Computer outs and other stuff can cause fragmentation of the hard drive, which a simple defrag can fix.
By the way, which operating system are you using? This helps me to figure out what tricks can be done. Like if the installation has become corrupted it can be fixed with a UnZoone uninstall that wipes the registry junk away.
Another question is what does it specifically say for an error in the crash window? Something along the lines of Error Code E0FOE is what you are looking for.
I am also taking a stab in the dark and assuming that you are using the Zune 2.0 software. If you notice any particular instances of it crashing like playing a certain file or doing a certain action it might be useful.
Once we can gather some more information on this crash a solution might be forthcoming.
I would also take a look at the
http://forums.zune.net/default.aspx?ForumGroupID=3 and if you need some help digging through it I will do so once I have more information so I know what I am looking for.
I find the most common reasons for a program crashing is A) Bad/Corrupt Installation B) Conflicting Software C) Problem in Software code D) Anti-Virus Conflict. Although it can be something totally different.