Gee Chris, you seem to have quite a collection of broken browsers

just tried nutscrape 4.6 a horrible browser...

indeed

italic with the promt, (I)
and then some text
and then closed it.. fine

so got

[*I]sdfsfsdfdf[*/I]

I have to admit that for about 10 minutes there I was really confused as to why the script would be putting asterisks into your tags... then I worked out what you were saying

then i used the buttons tounderline, italic and bold typed some text and then said close all. But i got:

[*/U][*/I][*/I][*/U][*/U][*/I][*/I][*/I][*/I][*/I]

This sounds like another problem with the array.push() and array.pop methods, which are used to store and retrieve the tag history. I can't reproduce it on the version of NS4.6 I have here, but hopefully the workaround will fix this for you.

The other thing is that pressing "close" makes the cursor go to the start of the text box which is pretty annoying...

This always happens with NS4.6, I'm afraid there's no way to position the cursor at the end of the text in that browser. It does pop to the end using later browsers though.