Polarizer doesn't want to rotate

I have a B+W 77mm MRC Circular Polarizer which I purchased in September, 2010. Until about 2 weeks ago, it worked fine. Then one day when trying to rotate the filter, I noticed it was unscrewing from the lens and not rotating. Upon investigation I found that I could not rotate the filter by hand. I've taken it to a photo store and they got it to rotate. But it is still very stiff. Has anyone else had a problem like this? What should (can) I do to free up the rotation?

FPP wrote in post #12390966
I have a B+W 77mm MRC Circular Polarizer which I purchased in September, 2010. Until about 2 weeks ago, it worked fine. Then one day when trying to rotate the filter, I noticed it was unscrewing from the lens and not rotating. Upon investigation I found that I could not rotate the filter by hand. I've taken it to a photo store and they got it to rotate. But it is still very stiff. Has anyone else had a problem like this? What should (can) I do to free up the rotation?

What's the warranty period on the filter?

By the way - you've been attempting to rotate the filter in the wrong direction. You should never rotate it in the direction of unscrewing it from the lens, because someday you'll drop it that way. By turning it in the opposite direction (clockwise while looking at the filter with the camera behind it) you'll make sure that the threads are fully engaged all the time.

Yes, you are correct about the preferred direction of rotation, but it wouldn't turn that way. So I tried the other and was aware of it becoming detached. Excellent advice none-the-less.

I just checked and it has a 10-year warranty. Thanks.