Will taking expired cetirizine tablets cause health problems, for about a year now and didn't think anything of the vinegar smell, expired 01/15?

Quite possible. Your age is one problem if you are 65 or older.Over prolonged usage you may get liver or kidney impairment. The vinegar smell is a warning that the drug has deteriorated. I would advise seeing your physician and discuses the taking of certirizine over such a prolonged time.