When you stained the wood, did you wipe off the excess? Sometimes an excess of stain on the surface can cause adhesion problems. If the table is a refinish and the spots look like small round circles then it sounds like silicone from furniture polish. If that is what it is it would have been better to clean most of that off before stripping the finish. The solution for silicone contamination is silicone. If you go to an automotive paint store ask them for a silicone control solvent and follow the directions. I use one called smoothie. It comes in a small squirt bottle like soft soap you just use a couple of squirts to a quart of finish. You really should find out for sure if it is silicone before you start using the additive and only use it if you have to. It might help if you would post a picture.I recently sanded and stained a tabletop...When completely dried I applied a light coat of poly..only to see it does not adhere well..It seems to be pooling in a lot of areas..?? any suggestions as to why.??