Sometimes when my cream is stored in the back of the fridge, I see those lumps, too. Nothing to worry about, unless it tastes spoiled. Then throw it out!

Thanks guys!
I just made ice cream with it and... it tastes delicious. So I guess it was fine after all.

If it smells fine then it should be okay to use. Also I might taste a little of it to make sure it has not curdled. And if the lumps are undesired try straining the cream through a fine mesh sieve.

Chances are the cream you have is fine. Perhaps it is not homogenized, which helps prevent separation. If the cream smells okay, then the lumps are likely small bits of butter. Depending on what you are using the cream for, you can strain out the lumps and use the resulting un-separated cream. Also, you can shake the cream to try and break up some of the lumps. Just keep in mind that shaking it may ultimately encourage it to thicken.

Good luck.