Collar causing hiccups?

I have an 8 month lurcher and have noticed that she gets hiccups about 3 or 4 times a day but only when she has her collar on (I've taken it off and walked her on her harness and she hasn't had them whilst it was off, put it back on and she hiccupped again).
She has a 1 inch leather collar and is loose enough to get four fingers under (my preference is three but it's a buckle collar).
Have any of you ever heard of this or experienced it happening? I'm thinking of trying a greyhound collar on her as I think it could be catching her a little.
I don't really like her naked in the house as she's still very boisterous with our 14yr old cat and also prefer walking on a collar (she doesn't pull, if the lead gets tense I just gently squeeze and she slows down).
I'm probably going to pop into the surgery and talk with the nurses when i walk her in a while to see what they think.
Thanks