I too have had this same issue for quite some time now.
iTunes Match will hang on this step for as much as one hour.
I have been back and forth with Apple support for almost two months.
I have spoken with three Senior advisors, and had my network data collected three times.
As it stands, after reviewing my data, the engineers sent me two common responses.
First they said it was network congestion due to the time of day.
Then they said it was due to my provider, needing to allocate more bandwith to the popularity of the service.
For the record, I have a high bandwith connection that is deicated to my house,
And I have 0 issues with any other network services.
After numerous troubleshooting, everything attempted, this has to be a server side issue.
The iTunes matching process more specifically, the "sending information to Apple" step,
Will sometimes take 1-2 seconds, but more often will hang for over 20 mintues, sometimes one hour.
Last night this sending step took 45 minutes, this afternoon, the sending step took 1-2 seconds.
iTunes Match has always worked for me in the past, I have been a subscriber since it's launch.
I have an Apple eco system for the entire house, network included, with no firewall or anything else interfering.
As a paying customer who has devoted quite a bit of time trying to solve this problem, this is unacceptable.
This thread is almost one year old from people all over the world, with no official response.
My advice is to call Applecare and report this issue, direct them to this thread.
Also I don't know if this is the best way to file a complaint, but please use this feedback form.
http://www.apple.com/feedback/itunesapp.html
I myself have had my case open about the issue regarding iTunes Match hanging for almost two months.