unseating rider

Question
I have an 8 year old Irish sport horse, she is a mare that I have had for 5 years. She is stabled during the winter and let out when the weather is fine and she is out all summer. As I dont have any land she is kept at a local riding school and is turned out as part of a group which she becomes quite attached to when she is in season. When I first got this mare she was in bad condition but had a lovely temprament and had some basic schooling, I have schooled a few horses previously all with success. She has come along greatly, she is regularly ridden both indoors and outdoors alone and as part of a group. I have competed her in showjumping competitions, one day events and cross country trials, and has been hunted a few times. She has always had a good attitude to these events and had never tried to unseat me during all her training until recently. As I am now in college I still ride her regularly but she had not been brought out of the riding school for over a year until last month. To get her back in the swing of things I brought her to a charity beach ride, some other horses from the riding school also went. She had never been to the beach before but at the start she was very calm and at ease but suddenly after about an hour she started to lunge into the air and gallop off. The first time this happened I was thrown above the saddle but regained my balance and control. This happened 3 or 4 more times, and she had become very upset. A while later we were standing still when a few horses started to canter away again she jumped right into the air, dropping her shoulder as she landed and I fell off. Once she was back home this behaviour stopped and I brought her to a cross country trial 2 weeks later. She was calm as we warmed up by the horse boxes and walked up to the warm up arena, I was walking around the warm up arena with 3 other horses she knew when without warning she leaped again and galloped straight for the wire enclosing the wire, I managed to stear her away from it but once I brought her back to a trot she launched again, throwing me off and underneath her, I ended up breaking my ankle. I will hopefully be back in the saddle soon and I would really appreciate some advice or explanation for this behaviour as she is a great horse and I would hate to loose my nerve. I thought that she was just upset by her surroundings the first time but the second time it happened she was quite calm and I found this confusing. I have had her checked by the vet, and have checked all her tack. Thanks so much for any help.

Answer
Hello,
Since you have already checked her tack and you know it is not a pain issue, we can assume that it is a herd issue. Does she get turned out with a herd often? I find that with show horses they can become less socialized because of their value, I would turn her out as much as possible. That being said, you need her to see you as her lead in a herd of two so she does not get upset when she see's a new friend leaving. Do you do any kind of ground work with her? How is she with plastic bags? Take an old whip and tie a plastic bag to the end, can you shake it all around her body without her flinching? Please give me a little more information on your ground work, or how you work her from the time you pull her out to the time you ride. She sounds like a great horse and you sound like an experienced rider, we just need to get an idea of what step was skipped over so we can make it clear to her.
Let me know your situation, I think some ground work with a bag or a flag will work it out.