Another reason for substituting the plate is that the ADSL filters which the internet providers give out are very cheap and seem to fail not infrequently. I've gained an unwarranted reputation as an internet genius by giving surplus ones to friends whose "internet won't work". I also suggest to them that buying a new faceplate will stop the problem in future.
It is reassuring when thing go wrong that this particular fault can be disregarded: I've never heard of an i-Plate failing... they seem to be made to a higher standard than the individual filters.