I went to my first meditation class last evening and it was wonderful!  The only problem is what I felt during my first meditation there and the "teacher" really didn't give me much insight.

She had us visualize our heart with a flower in the center, then the sun warming the flower, the flower growing and spreading love throughout our body.  I visualized all of this, but instead of feeling free and light, I felt REALLy heavy. Towards the "end" of the meditation, it got to the point where I was having trouble breathing and my body felt like lead. Once we opened our eyes, I couldn't move. Not a muscle in my body would move, I couldn't speak and I felt slightly sick.

Can anyone help me to understand what happened here?  Was it fear?

Did you inform the teacher?
Did she do anything to help you?
It sounds as though she was irresponsible towards her students, if something similar to this happens in my class I close the saharara point as quickly as possible, a tap straight down on the top of the head does it (you can do it yourself).
The classic for me was when I took a student to do some advanced Tai Chi in a circle of standing stones near where I live.
It went very well and as we were walking back down the hill he kept bounding higher and higher, saying he was taking off(it was like waching those moon landings), a quick tap on the head and he was fine again.
So I'll leave others to give their views but mine - for what it's worth, is this teacher is dangerous, stay away.

Thank you Prof. Akers   She didn't tell me very much when I explained what happened. She just told me that its possible it was my fear. I felt fine after a few minutes.

What do you think it was that I was experiencing?

It could have been reverie.
Sometimes you get in a state that is similar (and remember all experiences are subjective), you would feel fear if you never had it before, it's almost like you can touch 'god' .
My instructor thought that the emotion was so over whelming that it had to be avoided.
One school I went to used to come round and slap you on the back with wooden paddles - very hard, partially to waken you up and partiall to shake off these feelings.
Fear of anthing new is totally understandable, you never said about any other phenomina - taste, sound etc.
I'm not going to give any more information on that because that would colour your response.

1) Keep in mind that real insights rarely come on a silver plater and can arrive when you least expect it.
Too much expectation interferes with the process.

2) Even the worse of teachers have a lesson to learn.

AND

3)If you seek honestly and earnestly you will find exactly what you are looking for.