I have the same exact problem since I've updated to the last version. The complete error is:

<b>Fatal error</b>: Cannot redeclare cp_porttosqlite2() (previously declared in D:\Inetpub\Virtual\ameriaux\WWWROOT\CGI-BIN\cblog\serendipity_config.inc.php:15) in <b>D:\Inetpub\Virtual\ameriaux\WWWROOT\CGI ...