I'd had my phone for two days when I left for Europe on business. It worked flawlessly for the first two days, and I had set it up as a new phone. Left for Europe and turned off data so AT&T couldn't screw me. Got back, turned on data, and all seemed well for about 12 hours.
Left WiFi and in about an hour I suddenly got the "iTunes Match has expired..." message.After reading the posts here I checked. Somehow Match was suddenly turned off. Turned it back on, took about 1 minute on WiFi and it was working again.
To turn it back on I checked settings. There are several....and all must be enabled. Under "iTunes & App Stores" there's a setting for Match. Turn it on, choose what you want to download and then at the bottom of the page is "Use Cellular Data". It was off... how, I don't know.
Then, under "Music" in settings there's another "iTunes Match" switch and another "Use Cellular Data" switch. Match was on but the cell data switch was off. Turned it back on.
Checked under the other items... Videos, Photos, iBooks, Podcasts, iTunes U. Only Podcasts had a cell data switch. I almost never get podcasts on the road so I turned it off.
All seems to be working. I disabled WiFi, used it a bit, turned WiFi back on, off again.... no more problems that I can see. But, if it's truly a bug it may not show up in 30 minutes of use. At least I know where to go to turn all of it back on and it's only a minute or so to get it back.