I haven't experienced this with my one - but have you tried 'sweet' savoury foods - like peas, sweet potato etc. It might work.
Does baby take sweet food in the highchair - if so then I suppose it is unlikely to be the actual chair.
My little one did go off things like potato at about 7 months and so we just switched to star pasta and cous cous for his carbs - he is now Ok with potato again.
my 7 month old use to eat all food, sweet and savory but now wont eat the savory stuff. he takes the first spoon and then just keeps his mouth closed till I give him the bottle. this has gone on for about the last week or so. Ive tried leting him touch the food and it kind of worked the last few days but today nothing. he does eat finger food though, well sucks it abit!!! toasted cheese sandwich. weve only put him in his highchair for over a week, would it be that? dont think its teething. anyone else had the same problem?