Strange characters (character encoding?)

Hello,

For my website, I created my own search-engine (because it’s not totally word-pressed, there is also some own made stuff).

Now, when I query the wp database, words with special characters (like è é ? ê etcetera) look very strange:
for example:
????n
in stead of:
één

I gues this had something to do with character encoding or something. I don’t know much about that, and I can’t find out why the articles displayed in wordpress doesn’t contain the strange characters.

Anyone has a idea how I can fix this problem?

Thanks in advance,