Inserted strings get truncated when they contain german "Umlaute" like ä, ü, ö .... [URGENT]

[eluser]mradlmaier[/eluser]
Hello all,

I discovered following strange bug in my app:
I have a textfield. I enter a string which contains a german Umlaut (ä, ü, ö, etc.). When inserted in the database, the string is truncated before the germen Umlaut.

I am using MySQL and the collation of the column is utf8_general_ci. Does anybody know how to fix that?

Thanks for any hints,
Michael