I have limited knowledge only, but this could be a result of using an editor which lets some invisible marks in that file. In this case You can make them visible by using an hex editor. You as well would have to use a good utf-8 editor like notepad++ to encode the file as utf-8.
With the normal notepad You cant delete this mark and as well not see it.
Regarding the IE8 thing.
Did You change the answer box css or is it still the original one ?
May be this as well can be changed by using other css.
I thought I was using IE7 but no, I as well use IE8 and I do not have any differences between the different explorers, if You changed the css it could be helpful to see it one time, may be someone knows what to do.
EDIT: In my case everything validates fine at the beginning of the file at least.