Troublesome charset

Hi everybody,
I have a problem with my web applications.

When I try to perform an insert or an update query from a web page, Western Europe characters are not stored correctly in the database.
By the other hand, if I perform the SAME query from a DB tool (such as Toad), the characters are stored correctly... when I go back to the web page, though, they are still displayed in a wrong way.

So it looks like a request / response charset problem.

I tried to use different charsets (UTF-8, ISO-8859-1, WINDOWS1252) in IIS (".NET Globalization" section), in the web.config file, and in the machine.config file, butnothing worked.

I've been stucked on this problem for a long time already and I can't see a way out.
With the old server (IIS 6 and Windows Server 2003) everything used to work fine.

Any help or hint would be really appreciated,
thank you very much