Exactly which symbols are you trying to see that you cannot see now? Which font are you using in your editor and channel/query windows?
It might have something to do with the font you're using in your mIRC Editor.
- Go into your popup editor (Alt-P)
- On the menu bar
File
Font... - Select the font and attributes you wish to use while editing mIRC scripts.
- Click the OK button to save your changes and return to the editor.
I prefer FixedSys 9 because everything lines up nicely, but that might not be a good choice for you if you cannot see some of the symbols that FixedSys doesn't show except as little black boxes.