Had that happened to me before. I used two wide (not the normal thin ones) rubberbands. One for the lens barrel, and another for the filter ring. Then firmly gripped the lens barrel one, and twist the filter one - and it came off.
If your filter has not been knocked or dropped, the chances of getting it unstuck is high. It might be more difficult if the filter has been damaged or bended.
There is one thing to note when trying to remove stuck filters is try to apply EVEN force on all side when trying to turn the filter. That might be difficult to do using your hands since you will usually apply force from only two points - your thumb and index finger.
There are always filter wrenches you can use to separate them. However, the camera stores here do not seem to carry them as they are inexpensive items. I have two sets I bought last year from B&H and the set has helped a couple of CSers here unstuck their filters. If all else failed, send me a PM and we can arrange a time for you to come to my house to use the filter wrenches.
Yeah, when you try that, you are putting even pressure on all sides when turning the filter. TS might want to replace the cloth with a sticky matt that people use in cars. That will give you more friction when turning the filter.
I have similar experience and will advice you a method that is sure to work.
This method is by heat and expansion of metal approach.
you can use a soldering iron to heat up the UV ring metal. Leaving the lens un-heated. Once the heated ring is very very hot already ( so hot that you cannot use hand to hold on to it ), you then use a piece of cloth to twist the rings apart. Be sure that you heat up the ring evenly.