greek yogurt problems

Thanks. I trust the brand and agree it may be a temperature/storage issue.

I wouldn't trust Chobini in general.. I think I tried their yogurt ones and it tasted like a powder with sugar.
May be you should try a different brand? I have been buying fage for 3 years by now from the different groceries in different states and it has always been the same.
making your own is always a solution too of course.

I'm at our storm home on the wild west coast of British Columbia. The truck arrives every other day at the Co-op and many items have to be tossed because the 4-5 hour drive in the reefer truck means something meant to be cold was sitting next to a box of frozen or too close to the reefer unit. Tossed by the grocery manager.
Perhaps this batch of yogurt was either stored incorrectly or was in the truck incorrectly.
Mix it up to see if you can "dissolve" the lumps, or, put through a strainer.
As Sam says, if it smells ok, looks ok, tastes ok, it probably is okay. Yogurt by nature is intended to be a bit sour and tangy - but not make you sick .
IF in doubt- toss it. It's less money than a latte!

I have seen some Greek yogurt being slightly lumpy/curdled.
Of course it's much thicker than just plane yogurt. Does the lumpiness extend to the bottom of the container? It might be the supermarket didn't store it correctly and it lumped up on the top. I really don't know. If it tastes fine, smells fine, it should be fine to eat. Maybe even more tangy.

Try making some yourself...no really special equipment needed.
Just take a spoon full of the old yogurt and mix in milk that has been warmed and put in a warm draft place. I use the microwave oven, turned off of coarse, and sometimes on cold days/nights I put in a hot water bottle in the chamber for thermal mass. 24 hours later you have yogurt.