I recently loaded a few hundred files into iTunes, and it's going through the paces of matching and/or uploading those files. But I've run into a problem, the process becomes stuck on Step 3 and never advances after hours of execution.
After opening Activity Monitor, iTunes is taking anywhere from 300% - 400% CPU time, and an absurd amount of memory / active threads. Note that iTunes functions perfectly fine during this time, except for the iTunes Match process.
When I ran into this problem previously, certain songs were having trouble uploading. I had resolved the problem by creating an AAC version via the right-click options and deleting the original version. In these cases, I think the files were ALWAYS mp3.
However, the problem has resurfaced, but with a much more obnoxious issue. When iTunes Match appears stalled and exhibiting the same high-CPU issue, I open Activity Monitor, select iTunes and click 'Inspect'. Over on the Open Files and Ports tab, I see a number of sockets, network connections, and 3 open files. These files are not only m4a / AAC files, but have already been matched / uploaded.
These files will continue to show up each time I Force Quit and re-open iTunes, restarting the iTunes Match process. It isn't until I use the aforementioned workaround on the affected files that a new batch of files is shown, or I actually make some progress on the iTunes Match view. (At least until it hangs on another song...)
Why is iTunes opening, and more importantly hanging, on files it's already processed?