I had the same exact problem. I would set my imac to download a batch of songs by iTunes match, I'd go do something else and every time I would come back to a crashed computer. No "Force Quit" possible, just plain crashed. So I would start it back up and have a go again. Finally after several days, I realized that it was a handful of specific songs that were the culprit. Now I don't mind if there's a glitch with a few songs. It was the fact that it ALWAYS crashed my mac. Come on iTunes team!
I found this article on Apple's support siten which has you restart iTunes Match:
It fixed a couple of the songs, but still the crashing on the remaining dozen. It appeared that the download was trying to reconnect with a previous attempt and for whatever reason, it caused it to crash. So after lots of trial and error, here is the solution for downloading a song that won't download (I don't think this is on Apple's support site):
1. Start playing the song. The iTunes Match cloud server will be forced to reinitiate a new download.
2. Watch the grey bar creep to the end of the load.
3. Right-click and download the previously undownloadable track!
I've never seen this particular problem before, so I hope these suggestions will be helpful.
First you should make sure the OS file system is healthy. Before doing anything make sure your backups are up ti date. Then restart and hold down the CMD+r keys. Choose Disk Utility and run verify disk. If it encounters any errors click the "repair disk" button. After that is finished, restart. Now try downloading a few tracks at a time and see if the problem persists.
You can also delete the "iTunes Library.xml" file and let iTunes rebuild the file.
At any rate I would suggest nly trying to download a few tracks at a time, rather than hundreds or thousands.
On my old imac with 2gb of ram, OS 10.8.2 and iTunes 11.01 and a large iTunes library, I would find that I would quickly run out of memory. I eventually established that in the background album art was being downloaded to artwork folder - I established this by looking at activity monitor.
Basically I could do nothing with iTunes until this process completed. Download would stop - purchases as well as match. Once background process finished, the downloads finished.
I have not been able to resolve this issue. Ended up buy new imac - don't appear to have this problem I supposed because of much greater processing power!!!
One other thing about failed downloads, click on download icon - top right corner and delete failed downloads. Icon will only be there if there are items there.