数组提示错误:arr is undefined.(IE6,IE8,FF正常,IE7报错)

我定义一个5万多行的大数组, 在IE6、IE8、Firefox下页面都没有出错，但是在IE7下提示'optionArr' is undefined.
当我把这个大数组减小到32746行时就能正常显示页面，多加一行都会出错.
谁帮我解答下,谢谢!
var optionArr = new Array();
optionArr['channel_all'] = new Array();
optionArr['channel_12_12|035'] = new Array();
optionArr['channel_12_12|035']['12|035|035a_2|2|201|000405|000405aa'] = true; ....