Problem with some punctuation characters not correctly displaying

[stardotstar]

I have not been able to nail this down accurately enough to determine its exact scope but I am finding that I get lots of ? symbols instead of what should be pretty standard characters like '

But I find that when I post special characters almost all of them work fine... Yet sometimes the users post and I get entries in them like this:

"The other day I saw John aka ?slider? Blake at the field and he was..."

clearly the user was attempting to put something in inverted commas or single quotes but they did not translate.

I find that I can post almost anything ¢fi›‹€⁄∞§¶•ªº¢£™¡ and only get a few "?" - so does this mean that it has something to do with the client end character/language/font settings?

I note that here I can see all the special characters ie:

¡™£¢∞§¶•ªº
⁄€‹›fifl‡°·‚
(that was <option>+1-0 and then <shift>+<option>+1-0) No '?'s

but on my site I get:

?™??∞??•??
⁄€‹›fifl‡??‚

Can anyone tell me what they think is happening>?

TIA\Will