Open /conf/_admin.php and find this line:

$fileupload_maxk = '96'; // in kilo bytes

Then edit the value in quotes. 1024 would be 1 MB, 7168 would be 7 MB. Don't make this any higher than the PHP limit for your server.

Sorry,
i still have the problem with uploading bigger Files then 96 KB. But following the tips in this board, i changed the Line
$fileupload_maxk = '96'; // in kilo bytes
first to
$fileupload_maxk = '2048'; // in kilo bytes
then to
$fileupload_maxk = '1024'; // in kilo bytes
and finaly to
$fileupload_maxk = '300'; // in kilo bytes

nothing works. The limit is still on. Should i restart the Provider ;)

Greetings,