Hmof2 - it may well be related to a dairy allergy. A lot of recurrent ear infections are. The allergy results in excess mucus production which bungs up the ears and becomes infected.
My DS suffered very badly with ear infections and glue ear as a baby/toddler. We took him off dairy for 3 weeks at a homeopaths recommendation and he has never had an infection since. This was after almost constant infections!
His glue ear also cleared up in a matter of weeks and has never returned.
He does however have residual speech problems which may have been caused by having glue ear from such a young age and the sounds having been 'muffled'. It may have been something else that cause the speech problems so it is not entirely clear, even now.
I really would recommed that you try a dairy exclusion diet for a short period of time, it really did make such a difference to my childs quality of life.
BTW other signs of dairy allergy would be a constanly snotty nose and excess dribbling and drooling - nice