Re: Having trouble with a knot
Do you have the tool? They make tying a nail knot a 10 second job.
If you are having trouble with the coating of your line slipping off I would try and cut the last 5" off of it and try again, it may just be that the end of the line was water logged from not being sealed at the end. Put a dab of super glue on the end of the fly line when you are finished to seal it back up.
If that doesn't work I think the line may be in bad shape as cowdawg suggested.