Potty Frustration

Thanks to Sierra's one success at Jasea's Princess Potty Party yesterday (check out Chelsea's blog!), Sierra woke up this morning and wanted to wear panties. I thought, okay, we'll give this a go. It will probably work because there couldn't really be a more inconvenient time for me. Isn't that how it always works? So I told her she had to go potty and she ran into the bathroom and climbed on the toilet. Way to go, Sierra! This might be the day. She didn't "go" but I had to take Mackenzie to school and had to put her in the car anyway. Of course, I was worried she would pee all over her seat and was thrilled when we returned home and she still had dry panties. Woo hoo--it's going great! "We" sat on the potty again and still nothing. But I wasn't discouraged. She was dry for a good hour before she had an accident, which she was not happy about. I considered her concern to be progress and armed with salty snacks, juice, chocolate, books, and a potty movie we kept at it. Every few minutes I put her on the potty and sat with her looking at books, singing songs, watching a movie, etc., until 4 hours later she had had 6 accidents, not one success, and didn't seem to notice the pee running down her leg anymore. So, here is my problem. She will start to "go" and stop herself. I will run her to the potty and she will sit for a good long time, but won't finish. She'll get up and several minutes later have another "accident". How do I communicate the idea of going in the potty to her? She seems to know what to do and how to do it. She doesn't have any problem sitting on the potty or getting clothes off, etc. . I think her problem is that she doesn't want to "go" in the potty. Needless to say, she is in a pull up and we will approach this again in a couple of days when I have a few days with nowhere to go. I do think that for me, potty training is the worst part of motherhood and I have dreaded it since the day she was born. Aunt Mary, HELP ME!!!
On the brighter side, I did get a cute picture of a 3-year-old wedgie!! Is there anything cuter than a little half-tooshie hanging out of dry Mickey Mouse panties? And yes, she is standing on my new coffee table! One problem at a time, please! She wasn't peeing on it!