Itunes match constantly restarts

Question

I recently subscribed to iTunes Match and find that the match process never seems to finish - instead, it seems to finish Step 1, bog down in Step 2, then unaccountably switch to the iTunes Store, never getting to Step 3.  Instead, it goes back to Step 1, but begins that process at a point well past the beginning.  My song library had 1988 songs in it;  Match seems to get to 1982, hangs there for a bit and then restart.  If the cloud icon is any indicator, no more than 60 songs appear to have made it to the cloud.  There were 220 songs which had a gray cloud icon, indicating that Match has not yet processed them and another 34 items which had an icon of a cloud with a diagonal cloud running though it. 
In various combinations, Iand based on what I've read in related threads, 've done the following:
1. I've stopped and restarted Match several times. 
2. I've started iTunes by holding down the Option key when starting iTunes and specifically selecting the appropriate library (presumably, threre's a background reindex which is prompted by this action, but I won't swear to it). 
3. I've identified, exported and deleted all songs which failed the match.
4. I've logged out of and logged back into the iTunes Store with a valid Apple ID
The problem persists, and any help would be appreciated.

Answer 1

I am having the same exact problem. I had been using the service without incident for over a year and just started having this issue when replacing some of my MP3 files with higher quality M4P (ALAC) files. It's massively frustrating. I wish this problem had started before I resubscribed so I didn't fork over a wasted $25.
edit: using most recent versions of mountain lion and itunes.