Picture freezes for short time every 5 or ...

Ever since new,every time i try to watch a program using DT16300-16 picture is contantly freezing for maybe 1 or 2 seconds, every 5 or 10 seconds. i assumed this was probably a arial fault, but tested arial and checks out ok. Contacted manufacturers who were absolutely useless. Try this setting Try that setting. This has gone on for beyond the gaurantee period, and i think now if it cant be resolved i will bin it. Shame really because the box has rarely been used.