Thanks Eric. I'm going to use your isNameQuirk method. I like that it only does the actual work the first time you call it.
As an aside for anyone else following this, there is another issue I found in MSIE. If, you use the same string for the name when creating all of your buttons, and then change the name afterwards, MSIE will still see them as part of the same button group. In FireFox, changing the names after creation will change the button grouping as well.