Interesting question, MB, because people often say things like 'Oh, I hated languages at school' or even 'I can't do languages'...
I didn't 'hate' science as such, but it certainly wasn't my favourite subject. Mostly down to crap teachers. An exchange I still remember is:
Me (to physics teacher): Can you explain this question? (Working on past papers prior to doing O'level)
Teacher: No. I don't understand that one either. Go on to the next question!
WTF!
Same teacher in his alternative guise as a chemistry teacher told me I was 'thick, thick, thick, thick, thick!'. Great for the self-esteem!
Other reasons were more practical. I didn't like biology because it involved drawing diagrams of things, and I really really can't draw at all, so drawing something like a fish, say, was just a nightmare for me.
I hated chemistry because basically I was scared of chemicals and of getting burned. That sounds a bit pathetic, doesn't it. But at home we weren't allowed to strike a match or anything like that - in fact there was nothing gas in the house, so no flames at all. My mum had two brothers who were killed before she was born (aged about 6 and 8) in a barn fire and I think she was just paranoid about fire (she still won't light our gas cooker even now). So I was just terrified of having to light a bunsen burner. But obviously didn't want to admit to being scared, so just pretended to hate chemistry instead.
I liked physics, though.
Not sure this is much help in helping you to help kids nowadays not to hate science, though... Children with a paranoid fear of fire are unlikely to make chemists... LOL!
Tempted to start a parallel thread about languages.