Just a suggestion Kelvin, have you thought of seeing a casting coach to see if there is someting wrong with your technique. I realise it is a recent problem, but you may have developed a bad habit and not realised it. Sea Angler will give you the name of one in your area.
Suggest Strip/clean Reel, Use Red Rocket Oil To Start With New Line As Already Suggested, Avoid Using Cheap Line It Works Out Alot More Expensive In The Long Run. Rather Than Me Explain How To Tune Your Reel. Look On Neil Makellow's Web Site Or The Similar Article By The Same Author On Veal's Website. If You Follow His Instructions You Should Be Ok, If It Still Persists Get Some Casting Instruction. Keep Trying You'l Get There In The End.