I would guess it could be a cable or source issue. Is it a blu-ray player, satellite box, PC etc.....are there output settings on the source that you can change? Eg, sky tv, set it to output 720p or 1080i. Is there an amp in between source and projector.
If you post a more detailed explanation of your complete set up, start to finish it will be easier for someone to spot the issue.
If I went on to a car forum and said "my engine is making a funny noise, can you help?" Thats not really enough detail to go on. I'm not having a dig, just struggling to know what the route of the problem might be.