Like greeny said before, the same bug occures in text, and is still not fixed in 6.16.

Code:
dialog test {
  size -1 -1 225 148
  tab "1", 10, 1 1 221 129
  tab "2", 20
  tab "3", 30
  text "NoNameScript © 2004 by greeny && mute", 332, 28 50 125 8, tab 30
}


If I open Tab 3 directly after init, the & is shown correctly, but if I first open the second Tab and open Tab 3 then, there is this little square.

Suggestion:
Remove the alt-links from text. They are only useful in clickable items, I think, so we don't have to write two & to get one &.

using mirc 6.35 on WinXP Home SP3 and Windows 7